ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR STUDY, DEVELOPMENT, AND PRODUCTION OF FERROSPINELS APPLICABLE TO TUNING OF SEARCH RECEIVERS QUARTERLY PROGRESS REPORT NO. 6, TASK ORDER NO. EDG-6 Period Covering January 1, 1954 to March 31, 1954 Electronic Defense Group Department of ElectricAl Engineering By: D. M. Grimes Approved by: /.( d B. Hershenov H. W. Welch, Jr. C. F. Jefferson Supervisor B. T. Kimura D. W. Martin P. E. Nace L. Thomassen E. F. Westrum, Jr. Project 1970 CONTRACT NO. DA-36-039 sc-15358 SIGNAL CORPS, DEPARTMENT OF THE ARMY DEPARTMENT OF AR14Y PROJECT NO. 3-99-04-042 SIGNAL CORPS PROJECT 29-194B-O0 April, 1954

TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS iii TASK ORDER iv ABSTRACT vi 1. PURPOSE' 2. PUBLICATIONS AND REPORTS 1 3. FACTUAL DATA 2 3.1 Theory of the Magnetization Process 2 3.2 The Manufacturing Program 2 3.2.1 A Description of the Problem 2 3.2.2 The j' Material 4 3.2.3 Results of Firing Series I and II 6 3.2.4 Firing Series III 10 3.2.5 Firing Series IV 12 3.3 Low Frequency Measurements 12 3.4 P1 and P2 Contours 12 3.5 Experimental Determination of the Heat Capacity of 20-30 Nickel Zinc Ferrite 15 4. CONCLUSIONS 19 5. PROGRAM FOR THE NEXT INTERVAL 20 REFERENCES 21 DISTRIBUTION LIST- 22 ii

LIST OF ILLUSTRATIONS Page Fig. 1 Complex Permeability vs Firing Temperature 5 Fig. 2 Initial Permeability vs Core Type, f = 100 Me 7 Fig. 3 Initial Permeability vs Core Type, f = 200 Mc 8 Fig. 4 Initial Permeability vs Core Type, f = 500 Me 9 TABLES Table I Firing Temperature, ~C 10 Table II Heat Capacity of 20-30 Nickel Zinc Ferrite 17 iii

TASK ORDER Title: STUDY, DEVELOPRYENT, AND PRODUCTION OF FERROSPINELS APPLICABLE TO TUNING OF SEARCH RECEIVERS purpose of Task: To further the development of ferrospinels of different incremental permeabilities and low losses, with reference to specific applications of interest to the Signal Corps such as RF tuning units. Procedure s The approach to the general objective will include: a. The preparation, under controlled conditions, of specimens of different compositions; b. The measurement of parameters such as the incremental and initial permeabilities, the saturation inductance, the coercive force and the Q (figure of merit) at various frequencies; c. The interpretation of these magnetic parameters in terms of the composition, reaction temperature, pressure and other conditions in the preparation of the samples; d. The relationship of the solid state properties of the crystallite with the various measured magnetic parameters; e. Theoretical explanations, where possible, for the relationships found in d. above. Reports and Conferences: a. Quarterly Task Order Reports shall be submitted reporting technical detail and progress under this Task Order; b. Task Order Technical Reports of a final summary type are in general desirable and shall be prepared at the conclusion of investigations of each major phase. Such reports shall be prepared as iv

decided in conference between the Electronic Defense Group and the Contracting Officer's Technical Representative in the Countermeasures Branch, Evans Signal Laboratory. Personnel Electronic Defense Group: Project Physicist: Mr. D. M. Grimes Countermeasures Branch, Evans Signal Laboratory: Project Engineer: Mr. Leon I. Mond Components and Materials Branch, Squier Signal Laboratory Project Scientist: Dr. E. Both Comments: The classification of this Task Order as Unclassified shall not preclude the classification of individual reports according to the information they contain, as determined in conference with the Contracting Officer's Technical Representative. M. KEISER Chief Scientist, Countermeasures Division Contracting Officer's Technical Representative v

ABSTRACT Problems in ferrite manufacture are considered. The structure sensitive and structure insensitive properties of the ferromagnetic material are discussed. Intimate mixing of the constituents has been achieved by coprecipitation. The introduction of excess Fe203 resulted in both desirable and undesirable properties. These properties are discussed and an effort to reduce the undesirable properties is proposed. Pits on the surface of our rings are analysed. Additional data on Firing Series I and II are presented and analysed. Firing Series III, with pressing force, mixing, and firing temperature as parameters, and Firing Series IV, with calcining operations and composition as parameters, are outlined. A graphical means of calculating p1 and V2 from data obtained with the coaxial inductor is derived. vi

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN STUDY, DEVELOPMENT, AND PRODUCTION OF FERROSPINELS APPLICABLE TO TUNING OF SEARCH REhCEIVTERS QUARTERLY PROGRESS REPORT NO. 6, TASK ORDER NO. EDG-6 Period Covering January 1, 1954 to March 31, 1954 1. PURPOSE The purpose of this report is to sunmarize the progress made by Task Group 6 of the Electronic Defense Group from January 1, 1954 to March 31, 1954 on the Signal Corps Contract No. DA-36-039 sc-15358. The purpose of the task is to further the development of ferrospinels of different incremental permeabilities and low losses, with reference to specific applications of interest to the Signal Corps such as r-f tuning units. The proposed program of Task Group EDG-6 was outlined in previous progress reports. Only those items will now be reported which have been worked on during the period. 2. PUBLICATIONS AND REPORTS No publications were issued during the quarter. Dr. Welch, Messrs. Nace and Grimes attended a meeting at Squier Laboratories on 18 February; Mr. Jefferson attended a symposium on ceramic dielectrics and ferromagnetics at Rutgers niversity on 10 March; Mr. Nace attended.the annual IRE convention in New York ity from 22 to 25 March..,, ~~~~~~~~1

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 3. FACTUAL DATA 3.1 Theory of the Magnetization Process (D. W. Martin; D. M. Grimes) The theoretical studies of the magnetization process have been combined with the measurement of the reversible permeabilities. The report is currently being prepared that was expected to have been issued during the past quarter. It is now expected to be issued during the coming quarter. 3.2 The Manufacturing Pr gram (D. M. Grimes; B. Hershenov; C. F. Jefferson; B. T. Kimura; P. E. Nace; L. Thomassen) 3,2.1 A Description of the Problem. The problem of ferrite manufacture is two fold. First, there is the choosing of the proper gross chemistry for the desired system and second there is the proper choice of manufacturing parameters. Each choice must be dependent upon the desired final properties. For the application of interest to this program there are three specific magnetic quantities which it is desirable to be able to control. These are (a) the effective permeability as a function of frequency, (b) the magnetic losses associated with this permeability, (c) the temperature dependence of the permeability and its associated losses. These properties depend upon both the structure insensitive and the structure sensitive properties of the ferromagnetic material. The structure insensitive properties are magnetostriction, anisotropy, and saturation moment. The structure sensitive properties are the internal localized demagnetizing fields and stresses. In Section 3.1.1 of QPR No. 5, the quasi-reversible curve would be assumed to arise from the internal localized demagnetizing fields, the superimposed variations would be assumed to arise from the internal localized stresses. Thus the magnetic properties of particular interest to this program would in great measure be determined by the localized internal demagnetizing fields and the 2

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN localized internal stresses. Therefore, we chose a specific gross composition ferrite and are now attempting to optimize those characteristics which result from the structure sensitive properties. This part of the program could then be carried over to apply to specimens with different compositions. The internal demagnetizing factors will depend upon the grain size and the orientation difference between neighboring grains. The stresses will depend upon the annealing and upon the completeness of the solid state reaction. If regions existed where the cation diffusion was incomplete, the result would be localized differences in the degree of inversion of the spinel with resulting differences in lattice constant and thus large internal stresses. The latter effect would be expected to be important at the lower firing temperatures. At the higher firing temperatures cation diffusion will be more nearly complete.l Grain size will be large enough so that walls can move rather freely over wide regions with resulting high permeability and high losses. Cubical particles, one micron on a side, contain on the order of 1010 atoms. Therefore, the spinel reaction must be accomplished by cation diffusion over a large number of unit cells. If the oxides were intimately mixed before firing, the reaction would be completed at a much lower temperature. It is known that the coprecipitation of ferrous and ferric hydroxide produces a precipitate that changes color and becomes ferromagnetic shortly after its formation. We have coprecipitated iron, nickel, and zinc with Na2C03 and have found that the- precipitate was slightly magnetic after being dried at about 1100 C and was quite magnetic after heating to 350~ C. This introduces the possibility of grain orientation by application of a magnetic field during the firing. The Curie temperature for the' material we are now making, 20 mole % NiO, 30 mole % ZnO, and 50 mole $ Fe203, is around 250~ C.

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 3.2.2 The j' Material. During the preparation of Firing Series II an error was made in the composition of the material described as type j. This material, hereafter called j', was composed of a nickel ferrite and a zinc ferrite. The zinc ferrite contained 60 mole % Fe203 and 40 mole % ZnO instead of the usual 50-50 ratio. Fig. 1 shows the variation of [l and I2 with firing temperature for this material at a frequency of 2 minc/sec. The result is a ~Q product of around 5 x 104 at this frequency. The material looked very promising since (a) it possesses a large pQ product and (b) the firing temperature is sufficiently high to eliminate any differences that might arise from differences in green density, in minor temperature deviations in the oven, etc. However, it was found that the material contained about 4 mole % ferrous iron. Associated w|ith the ferrous iron content is a high Richter Type3 after-effect which makes the material unusable. We are currently making an effort to produce similar material without the high ferrous iron content by replacing some of the nickel with lithium to prevent ferric ion reduction. CWe will also use replacement by sodium ions and the addition of pentavalent vanadium as an internal oxygen source. However, it is known that magnetite has a negative magnetostriction and most other ferrites a positive magnetostriction. The composition of j' is very near one which gives zero magnetostriction according to Harvey, Hegyi and Leverenz.2 The presence of a low value of magnetostriction results in a small value of the coefficient' in the differential equation of motion for the domain wall (Eq. 32, p. 15, of QPR No. 5) and thus in a high Q. Therefore, the high Q may arise from the ferrous ions we are trying to eliminate.

G*tdVtZZ.IJ ZL-99-V OL6-1V 380 24 340 20 1300 133 164 )w WJ I S 12 60S 112 (3 140 >z w 220 8 59 W 10 - 4140 / 0 1150 1200 1250 1300 1350 1400 FIRING TEMPERATURE (~C) 115 120 125 130 135 140 CODE DESIGNATION FIG I COMPLEX PERMEABILITY VS FIRING TEMPERATURE ]' MATERIAL f: 2 Mc

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 3.2.3 Results of Firing Series I and II. The density and permeability of some of the cores of Firing Series I and II were given in QPR No. 5. Sufficient data are not yet available to determine how much variation is present between the different core types manufactured in each series or for a comparison between series. Figs. 2, 3, and 4 show i1 versus material types a, c, e, f, g, and h, as defined on p. 18 of QPR No. 5, at different frequencies. These should be interpreted in conjunction with Figs. 11, 12, and 13 of that report. When interpreting the data of Figs. 2, 3, and 4 it is necessary to keep in mind that each plotted point on a curve represents measurements obtained from a different core. Since there are fluctuations in the properties of core subjected to the same manufacturing parameters, the results will deviate from a smooth curve. Present values of I2 are not considered sufficiently accurate. Therefore, a better coaxial inductor has been made together with modifications of measurement analysis to obtain ~2 Comparison of the frequency spectrum with the equations of Section 4.3 of QPR No. 5 is being undertaken. The permeability curves versus the firing temperature (Figs. 2, 3, and 4) indicate that the reaction which allows wall movement and produces a high value of permeability below resonance is nearly completed at a firing temperature of 12000 C. That the frequency spectrum actually undergoes a resonance can be seen from the negative value of susceptibility at 500 mc/sec for cores fired at temperatures higher than 1150~ C. As was expected, the permeability fall-off with frequency of the cores fired below 10000 is much smaller than those fired above. Although accurate data is not available at the moment, the Q of the core is satisfactory only for those cores fired at a low temperature. Once again, as expected, the cores whose characteristics are most.... 6

9Z!-!~ j-99-V OL6-' I 3 38 36 I 13500C \/'-4 I,,, \' ",\ \ /! 34 32; /~~~~~~~~~ 30\ 30 / 13000C 12500C 8200-C 28 - 1 1500 I- \ 26 I \ I \ w 024 i w i 4 12 1050 10 - 8 J~~~~~~~~ 66 i - \ 9000C )2 N8500C 0 _ I~ ~ " —-- -\ 2 o I\,,~, loooce / \r~ —- 5~ 8?__~150~C H A C E F G H CORE TYPE FIG 2 INITIAL PERMEABILITY VS CORE TYPE f=I00 Mc

f pQ8dLZ iSJ tL-99-v OL6-W 12 ~ 11500C /f~~~ = 200 12000C J8 co 10500C w // I \~ —~ —-— ~ I900C H A C E F G H CORE TYPE FIG 3 INITIAL PERMEABILITY VS CORE TYPE f = 200 Mc

tfhdVJ..Z U.=E 2 ~-99-V OL6-14 5 10500C 4'IOOOC /~~~~~~~~~ 7' 91100CC /~ I~~~~~~~~~~~~~~~~~looopc.....,- I950"C 33 7r ~ K9000C w 8500C 13000C -~~~~~~~~~~~~~~.-.-._..._ 1350~ C 12000 C,I~~~~ -~~~~~~~ ~12500C 01 H A C E F G H CORE TYPE FIG 4 INITIAL PERMEABILITY VS CORE TYPE f = 500 Mc

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN desirable at low frequencies are those cores which were fired at a high temperature producing a large amount of wall movement. 3.2.4 Firing Series III. The object of Firing Series III was to determine the effect of the pressure on the original "pill" and the effect of different mixing procedures. The code designations for the variations will be: -| TABLE I FIRING TE-PTiATURE, ~C Pressing Force, lbs. 1000 1050 1100 1150 1200 1250 250 162 170 178 186 194 202 500 163 171 179 187 195 203 1000 164 172 180 188 196 204 1500 165 173 181 189 197 205 2000 166 174 182 190 198 206 3000 56 64 72 80 88 96 4000 167 175 183 191 199 207 5000 168 176 184 192 200 208 6000 169 177 185 193 201 209 Mixing: a) Ultrasonic 300 kc/sec 210 214 218 222 500 kc/sec 211 215 219 223 750 kc/sec 212 216 220 224 1000 kc/sec 213 217 221 225 b) Ball Milling 10 min. 226 228 230 232 24 hrs. 227 229 231 233' For an explanation of the code system see p. 18 of QPR No. 5. 10

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN The numbers represent the code designation for each material. To indicate a nickel-zinc ferrite, all numbers carry the prefix A. Because the dies stick enough to make the total force applied to the die quite different from that felt by the material the green density of each core was measured and taken as the real criteria of the pressure. The variation of green density at a constant applied force can be seen from the example of 3000 lbs. applied force. Here the green density was measured as: 2.1l; 2.28; 2.33; 2.37; 2.26; 2.28; 2.36; 2.29. The ultrasonic mixing was done for us by the General Electric Company. They were insonated for one minute at 300 kc/sec, then at the frequency listed in Table I for another minute and returned to us. A period of perhaps a week elapsed between the insonating and the removal of the oxides from the slurry. It is not known how much the material settled. The following observations were made on the surface of the material mixed by the different methods. The material ball milled for 24 hours and fired at 11500 C showed indented regions up to a millimeter in diameter with a metallic luster as compared with the brownish black of the rest of the core. These indentations ranged in size down to as small as could be seen on the 500 power of the microscope. The material which had been ball milled for shorter periods of time and that had been insonated showed fewer large holes and more small holes. The 24 hour ball milled material showed about 10 spots per cm2 with a diameter of over 0.5 mm, and about 200 spots of the order of.01 mm. The 10 minute ball milled material showed about 1 large spot per cm2 and around 400 of order.01 mm diameter. The insonated material looked very much like the 10 minute material.

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN The pits are seemingly a product of shrinkage due to grain coagulation. Thus the large pits presumably occur for a reaction nearing completion. It also appears from preliminary permeability measurements that the better the material is mixed, the larger the fraction of material reacted at a given temperature, The difference between ball milling for 6 and 24 hours is inconclusive as could be expected. 3.2.5 Fir.in Series IV. Firing Series IV will investigate (a) the effect of completing the reaction of the individual spinels prior to mixing the spinels as compared with mixing of the original oxides. This will be, in essence, a variation of the type i material with a longer and higher calcining temperature. It will also (b) both investigate the effect of additions of univalent material to keep the iron in the ferric valence state when more than 50 mole % iron is introduced and the effect of adding pentavralent vanadium. 3.3 Low Frequency Measurements (B. Hershenov) The manufacturer of the permeameter is as yet unable to furnish a primary core which will allow measurements in the frequency range 100 to 800 kc/sec for the type B permeameter. Therefore, we are attempting to carry out these measurements at given fixed frequencies in this range by winding a General Ceramics type Q core as the primary. This core gives agreement with the core supplied by the manufacturer within 6% at 1 mc/sec. It has not yet been evaluated at lower frequencies. 3.4 P1 and P2 Contours (P. E. Nace) The calculations required to determine permeability and losses of a ferrite toroid from impedance measurements on the coaxial inductor are laborious. If Zg and Qg are the impedance and phase angle of the coaxial inductor as measured on the Hewlett-Packard VHF bridge at a frequency f, one must make the following calculations: 12

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN Zg' = Zg (1 + a) where a is a small percentage correction obtained (1) from calibration curves supplied by the manufacturer. g = Qfg + Qc where 0 is a small correction likewise obtained (2) fo c c from the manufacturer's calibration curves. fo = 100 megacycles/sec. ZL2 (Zg' cos 9g')2 + (Zgt sin Qg' - Zg')2 (3) 1 + Zg'g' sin Qg + [ZgZ cos g - 22 Zg Zg' cos Og' L sarcta sin g Z + arctan Zg (i) Zg' cos g' 1 Zg sin + 2 sig' Z2 0 where Z is the characteristic impedance of the short transmission line joining the toroidal section of the coaxial inductor to the point of measurement in the bridge. Zgt" = Zo tan 2,T, where e is the length of the transmission line. fo Finally: p1 = 1 + r2 (ZL sin L- ZA) (NKS units) (5) 4rrf t nr1 foZL cos L (6) r2 4hf t en r1 Here ZA = odf en F-* ro and ri are the outer and inner radii of the coaxial inductor. d is the length of the toroidal section of the coaxial inductor. t = the thickness of the core. r2 and rl are the outer and inner radii of the core. For all of our cores- is a constant. 13

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN These calculations are too long if one is faced with hundreds of measurements. Fortunately, at a given frequency the factor t is the only quantity that changes with measurements on different cores. Therefore charts can be made in terms of contours involving P1 and P2 which are defined by: P1 = t(l - 1) and P2 = t p2 The contours are computed from the following implicit expressions which can be derived from the formulas given above: P1K + ZA + Zgt' 1 eZ it (PiK + ZA - P2K cot Gg') Zo Zg' cos 1 P2(8) 1I- 2g (P1K + ZA + P2K tan Qg') Zo2 where K 5 n 2 fo rl The contours are calculated as follows' 1. Select a value for P1 and a value for P2. 2. Guess a value of Gg' 3. alculate = arctan sin 1 and compare Q1 with 9g'. This procedure is repeated until Q1 is obtained equal to Qg'. Then one calculates Zg' from either Eq. 7 or 8. l. Next, one calculates Qg and Zg from Eqs. 1 and 2. l. Finally, one plots the calculated data on the Zg-Qg plane, joining points of constant P1 to form P1 contours and similarly for P2 contours..... )

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN One need only take the measured impedance Zg and phase angle Qg, use the P contours to obtain PL and P2, and divide by t to obtain [l-l and 2.' P-contours have been calculated for two frequencies, 50 and 200 mc/s. They will be calculated for some additional frequencies. They will result in a material savings of time and labor. 3.5 Experimental Determination of the Heat Capacity of 20-30 Nickel Zinc Ferrite E. F. Westrum Jr.) The heat capacity of this material was determined over +the range 5.5 to 3000 K in the adiabatic calorimeter described in Section 4.57 of QPR No. 1, Task Order EDG-6. The cryostat and manner of operation are also described in the same section. The actual sample contained (laboratory designation W-5) is described more fully in Section 3.32 of cQPR No. 2, Task Order EDG-6. The pressure of helium gas in the sample container was 3.8 cm. similar to that used during heat capacity measurements on 10-40 Nickel-Zinc Ferrite. The sample (code h8-70) was prepared by this task group. It was fired at 12000 C for four hours, then cooled at 600 C/hour in an oxygen atmosphere to 4000 C. Although the same cooling rate was employed to the ambient room temperature the oxygen flow was discontinued below 4000 C. Analysis indicated 0.2% by weight ferrous iron present. To correct this situation the material was reground, refired to 9000~ C for 85 minutes and cooled in oxygen as before. The sample was prepared from C.P. grade oxides mixed by weight to the following composition: Fe203 66.984% NiO 12.533% ZnO 20.483/

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN corresponding to a theoretical 46.84% iron. Determination of the total iron present by titration TJith potassium dichromate indicated 46.8 + 0.1% total iron.'F The determination of ferrous iron in the final material was less than 0.1% by weight. The empirical chemical formula therefore may be represented as (Niho 4zno.6) Fe203 with a gram formula weight of 238.404 grams. The sample employed for the heat capacity measurements weighed 203.4344 grams, The heat capacity data are presented in Table II, per gram formula weight, in terms of a defined thermochemical calorie equal to 4.8l40 absolute joules. The values of the heat capacity are believed to be accurate to within 0.2% above 350 K with an uncertainty which increases to about + 0.5% at 200 K and to several percent at the lowest temperatures. These data have been tabulated as Cs (equilibrium values at the 3.8 cm pressure of helium within the calorimeter) and hence are virtually identical with C (heat capacity at constant pressure) values and have been corrected for curvature to true heat capacities. The graphical presentation of the heat capacities (Figure 17 of QPR No. 5) reveals that the heat capacity is a very smooth function of the temperature and that the data are very precise. Comparison of these data with those made earlier on Ferramic-E indicates a generally parallel behavior in the two materials of somewhat similar composition. A slight hump in the heat capacity appears in the region of 100 K. This is however, small in comparison with that found in the 10-40 nickel-zinc ferrite. Plans for the immediate future include preparation of samples and determination of the heat capacity of 5-h5 and 15-35 nickel-zinc ferrite materials ~ The determinations were made by Mr. C. F. Jefferson. 16

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE II HEAT CAPACITY OF 20-30 NICKEL ZINC FElRRITE (NiOo.4Zn0O.6) Fe203 Gram Formula Weight = 238.404 0~ C = 273.16~ K SERIES I __ AT, T~K cal(gm form.8wt)AlTdeg K 63.23 5.592 6.324 69.11 6.167 7.354 75.83 7.285 8.556 83.16 7.374 9.900 91.49 9.270 11.42 90.54 7.468 11.25 98.30 8.063 12.61 106.78 8.890 14.10 115.28 8.120 15.59 123.12 7.553 16.93 130.70 7.608 18.19 138.60 8.193 19.45 147.06 8.718 20.77 155.74 8.652 22.06 164.52 8.892 23.30 173.47 9.012 24.51 182.58 9.207 25.65 191.87 9.372 26.77 201.18 9.239 27.83 210.40 9.203 28.83 219.59 9.177 29.73 228.65 8.940 30.61 237.58 8.921 31.41 246.56 9.062 32.19 255.62 9.050 32.91 264.65 9.008 33.62 273*70 9.094 34.30 282.71 8.946 34.92 291.70 9.042 35.52 300.83 9.217 36.09 17

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN TABLE II (continued) SERTIES II T, OK.....AT, OK cal(gm form. 8wt)-ldeg, 1 4.50 0.267 0.0682 4.87 0.623 0.0659 5.65 1.096 o0o845 4.75 0.668 0o0698 5.58 1.Q87 o.0818 5.49 1.188 0.0792 6.66 1.287 0.1052 7.87 1.183 0.1420 8.96 1.o060 01836 10.00 1.047 0.2317 11.11 1.202 o.2569 12.38 1.367 0.2950 13.77 1.449 0.3415 15.27 1.555 o.4o18 16*86 1.629 0.4653 18.52 1.704 0.5393 20.28 1.813 o0.6274 22.17 1.982 0.7363 24.37 2.422 0.8862 26.80 2.447 1.073 29.37 2.697 1.304 32.14 2.831 1.591 35.29 3.458 1.956 38.67 3.313 2.394 42.16 3.661 2.879 46.10 4.215 3.468 50.74 5.044 4.204 55.57 4.632 5.003 60.34 4.885 5.818 65.57 5.576 6.376 18

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN to survey the nature of the low temperature thermal anomaly. 4. CONCLUSIONS There are two basically different types of processes which determine magnetic behavior, i.e. structure sensitive and structure insensitive. For control of the finished product more knowledge of how to control the structure sensitive properties is essential. Therefore, we have chosen to pick a specific composition and to see That could be done -with the structure sensitive effects. These we believe to depend upon the internal demagnetizing factors and the internal stresses. From Firing Series I we conclude that the variation in properties with temperature is so rapid in the region of 1050 to 12000 C that it is necessary to use rather elaborate methods of temperature control. At higher temperatures high values of permeabilities exist, but the CQ falls rapidly wsith frequency above a few megacycles. The exact value of the frequency where the fall off occurs is controllable to a degree. This value, for a given composition, usually decreases with increasing firing temperature. In this temperature region, the green density and thus the pressure is unimportant. Cores to be used above the frequency of rapid drop in Q must be fired at a low temperature. This does not preclude the possibility of firing an initial powder at a high temperature, mixing with oxides and refiring at a low temperature. In this temperature region the permeability spectrum indicates magnetization by rotation. Oxides mixed by chemical coprecipitation as hydroxides and carbonates become slightly ferromagnetic at 1100 and buite magnetic at 3500 C. 19

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 5. Pi{OGRAIi FOi' THE NEXT INTERVAL Analysis of the firing series will continue. The high frequency measurements will be considerably speeded by the P contours. The effect of green densities upon low fired material is being examined from the cores of Series III. Series IV will continue, miuxing by chemical coprecipitation will be carried to the point where several cores will be tested. The future program will depend upon these results. 20

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN REFERENCES 1. Kittel, C., Introduction to Solid State Pysics, John Wiley and Sons, New York, (1953), Pg. 309 and 3140 Mott, N. F. and Gurney, R. W., Electronic Processes in Ionic tals, Oxford Press, Clarendon, (1948), Pg. 33 2. Harvey, R. L, Hegyi, I. J. and Leverenz, H. W., Ferromagnetic Sinei s for Radio Frequencies, RCA Review 16, No. 3, (1950), Pg. 321-363, Fig. 21 3. Wyn, H. P. J. and van der Heide, H., A Richter Type After-Effect in Ferrites Containing Ferrous and Ferric Ions, Rev Mod Phys 25, (1953), Pg. 98-99 21

DISTRIBUTION LIST 1 Copy Director, Electronic Research Laboratory Stanford University Stanford, California Attn: Dean Fred Terman 1 Copy Commanding Officer Signal Corps Electronic Warfare Center Fort Monmouth, New Jersey 1 Copy Chief, Engineering and Technical Division Department of the Army Washington 25, D. C. Attn: SIGGE-C 1 Copy Chief, Plans and Operations Division Office of the Chief Signal Officer Washington 25, D. C. Attn: SIGOP-5 1 Copy Countermeasures Laboratory Gilfillan Brothers, Inc. 1815 Venice Blvd. Los Angeles 6, California 1 Copy Commanding Officer White Sands Signal Corps Agency White Sands Proving Ground Las Cruces, New Mexico Attn: SIGWS-CM 1 Copy Signal Corps Resident Engineer Electronic Defense Laboratory P. O. Box 205 Mountain View, California Attn: F. W. Morris, Jr. 1 Copy Mr. Peter H. Haas High Frecuency Standard Section Central Radio Propagation Laboratory National Bureau of Standards Washington 25, D. C. 75 Copies Transportation Officer, SCEL Evans Signal Laboratory Building No. 42, Belmar, New Jersey For - Signal Property Officer Inspect at Destination File No. 25052-PH-51-91(1443) 22

1 Copy H. W. Welch, Jr. Engineering Research Institute University of Michigan Ann Arbor, Michigan 1 Copy Document Room Willow Run Research Center University of Michigan Willow Run, Michigan 11 Copies Electronic Defense Group Project File University of Michigan Ann Arbor, Michigan 1 Copy Engineering Research Institute Project File University of Michigan Ann Arbor, Michigan 23

UNIVERSITY OF MICHIGAN 3 9151110101111III i11i 11111111111111 1 3 9015 03026 8976