the gyromagnetic ratio of supermalloy
TRANSCRIPT
P H Y S I C A L R E V I E W V O L U M E 89 , N U M B E R 3 F E B R U A R Y 1, 1953
The Gyromagnetic Ratio of Supermalloy
G. G. SCOTT Research Laboratories Division, General Motors Corporation, Detroit, Michigan
(Received September 24, 1952)
The gyromagnetic ratio of supermalloy has been determined by a highly refined magneto-mechanical method. The value obtained is 1.030±0.001 times the mass-to-charge ratio of the electron. Within the limits of experimental error, this is the same value as has recently been reported for pure iron.
INTRODUCTION
IT has been known for some time that the gyromagnetic ratio of a material determined by micro
wave techniques does not agree with the value determined by magnetomechanical methods. In an earlier paper1 the author published values for the gyromagnetic ratios of Fe, Co, and Ni, as determined by a highly refined mechanical method.2 In discussing these results with Dr. C. Kittel he suggested that this work be extended to include supermalloy since unusually sharp absorption lines are obtained by microwave methods for this material.3 Arrangements were
TABLE I. Condensed data for the determination of the gyromagnetic ratio of supermalloy.
Date
Dec. Dec. Dec. Dec. Tan. Tan. Tan. Tan. Tan. Feb. Feb. Feb.
3, 4, 5, 6,
18, 21, 22, 24, 25, 4, 5, 8,
'51 '51 '51 '51 '52 '52 '52 '52 '52 '52 '52 '52
Double amplitude
change per
reversal d (cm)
0.03562 0.03571 0.03566 0.03563 0.03528 0.03546 0.07395 0.07454 0.07420 0.07356 0.03573 0.03534
Element current
ie (amp)
0.004311 0.004309 0.004310 0.004310 0.004308 0.004309 0.009011 0.009012 0.009012 0.009011 0.004312 0.004311
Element magnetic moment
Me (amp cm2)
23 154 23 147 23 149 23 150 23 056 23 147 48 370 48 375 48 377 48 372 23 163 23 156
Period P (sec)
26.937 26.925 26.923 26.936 26.927 26.946 26.951 26.928 26.950 26.928 26.941 26.919
Average
Gyromagnetic ratio in
terms of m/e
for the electron
1.032 1.036 1.034 1.033 1.027 1.028 1.025 1.034 1.029 1.021 1.035 1.025
1.030
Area summation of element winding: 75 378. cm2
Moment of inertia: 210.52 gram cm2
Length of light beam: 1589.2 cm
1 G. G. Scott, Phys. Rev. 87, 697 (1952). 2 G. G. Scott, Phys. Rev. 82, 542 (1951). 3 W. A. Yager and R. M. Bozorth, Phys. Rev. 72, 80 (1947).
therefore made through Dr. S. O. Morgan whereby the Bell Telephone Laboratories very kindly furnished the author a heat treated supermalloy rod 1.5 cm in diameter and 22 cm long. This rod was wound with a magnetizing winding and supported as a torsional pendulum as indicated in reference 2.
RESULTS
The results obtained for this supermalloy sample are based on readings taken on 12 different days. On each day four runs were obtained—one for each of four azimuthal positions separated from each other by 90°. This method eliminated errors caused by magnetic coupling between any small uncorrected fields and the magnetized sample. To eliminate any possible errors caused by the magnetizing current passing through the suspension system, readings were taken on alternate days with opposite positions for the small reversing switch located on the pendulum system.2
The value for the gyromagnetic ratio of supermalloy as determined in this series of experiments, is (1.030zt:0.001)m/£. The data from which this value has been calculated are condensed and tabulated in Table I. This value corresponds to a Lande factor of 1.942. Within the limits of accuracy of these experiments, this is the same value as has previously been reported by the author for the gyromagnetic ratio of pure iron (1.946).
It will be noted that the gyromagnetic ratios as determined by microwave techniques are also very nearly the same for both iron and supermalloy, and that the magnitude of the departure from 2 is very nearly three times as great in microwave experiments as it is in the present magnetomechanical experiments.
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