Yoshikazu Sugiura

Exchange Interaction and Cubic Crystal Field Splitting Parameter of Fe3+ in Spinel Structure

The line widths of paramagnetic resonance absorption of Fe 3+ ions in MgAl 2 O 4 and ZnAl 2 O 4 polycrystals and of Mn 2+ ions in ZnAl 2 O 4 , having the same spinel crystal structure as ferrite, are measured as a function of concentration. The cubic crystal field splitting parameters a of Fe 3+ ion at A - and B -sites are determined from the line widths extrapolated to zero concentration: a A =1.0×10 -2 cm -1 and a B =3.1×10 -2 cm -1 . a B / a A =3.1. On the other hand, the magnitudes of exchange integral between Fe 3+ ions in A - and B -sites or in B - and B -sites are estimated from the decrease of line width due to exchange narrowing as the concentration increases, namely, J A B / g β=1.32×10 5 Oe and J B B / g β=1.90×10 3 Oe. The Curie temperatures obtained from the exchange integral are in agreement with the Curie temperatures of Mg-ferrite and Zn-ferrite measured experimentally.

Magnetostriction of Yttrium Iron Garnet

An adnesive strain gage was used to measure the magnetostriction of polycrystalline yttrium iron garnet. The relative change in length was plotted against the applied magnetic field. From this curve the saturation magnetostriction constant Λs = --(3.7 plus or minus 0.5) x 10-7 was obtained. This small value appeared to be explained by dipolar interaction.

Magnetic Anisotropy of Iron-Cobalt Ferrite Measured by Ferromagnetic Resonance

The magnetic anisotropy of iron-cobalt ferrite is studied by means of ferromagnetic resonance. The cubic magnetic anisotropy K 1 / M and the uniaxial magnetic anisotropy K T / M induced by heat treatment in magnetic field are measured in the temperature range between 70°C and 250°C. The secondary peak observed in the ferromagnetic resonance of iron-cobalt ferrite are explained by the domains having different orientation of uniaxial magnetic axis. From the experimental results g -factor of iron-cobalt ferrite is determined to be 2.86. The temperature dependence of g -factor has not been observed within limits of errors.

A Flow-Meter in Vacuum Technique

A direct reading flow-meter for the measurement of Q -value in vacuum technique is described. The principle of the meter is to measure the force exerted on a disc placed in a vacuum piping. The kinetic theory shows that the force acting upon the suspending plate, due to the thermal motion of molecules, is stronger than one supposes and this is proved by the experiments. Flow-meters of suspension type are made and tested. The highest sensitivity available is 1×10 -3 µHg. litre/sec per 1 mm. of scale. The application of this meterto measurement of pumping speed, measurement of desorbed gases, vacuum drying and leak detection are described.

Experimental Studies on the Force exerted on a Disc placed in a Flow of Rarefied Gas

Uyeda has devised a flow-meter in vacuum technique [Uyeda & Sugiura, J. Phys. Soc. Japan 8 (1953) 99], whose principle is simply to measure the force on a disc placed in a pipe through which a rarefied gas flows. As a basic study of the meter, the force was measured under various conditions, namely, the pressure of the flowing gas, the diameter of the disc, and the position of the disc along the radius of the pipe being varied. The results of the measurement are shown in figures and expressed by empirical formula. The results here obtained are in agreement with theoretical expectations for Knudsen and Poiseuille flow. In the Knudsen flow, it is confirmed that the assumption of diffuse reflection of molecules on the disc is adequate. In the intermediate flow case between Knudsen and Poiseuille flow, the force shows an anomalous behaviour which seems to have some correlation with the phenomena observed by Knudsen [Ann. d. Phys. 28 (1909) 75] and others.