S. Mitsudo

Spin-wave resonance in ferromagnetic coupled Co/Cu multilayers

Abstract FMR experiments have been performed on [Co(50 A)/Cu(4 A)] 20 multilayers at room temperature by using an X-band ESR spectrometer and a series of spin-wave modes have been observed when an external field was perpendicular to the film plane. We have analyzed these spin-wave modes by spin-wave resonance theory of multilayers and obtained the interlayer exchange coupling constant.

Submillimeter wave ESR measurement of LaMnO3

Abstract High-field magnetization measurements up to 40 T and submillimeter wave ESR measurements in frequency range from 95 to 762 GHz have been performed on a stoichiometric single crystal of LaMnO 3 . At 4.2 K, the induced magnetization curve shows nonlinear increase up to H c = 21 T for H ‖ b and linear increase above H c . This result suggests that the antiferromagnetic easy axis is the b -axis. For H | b , several ESR lines are observed at 4.2 K. The obtained frequency-field diagram shows these lines are the antiferromagnetic resonance with the uniaxial anisotropy.

Structural and magnetic properties of Ni2In type (Mn1 − xNix)65Ga35 compounds

Abstract New intermetallic compounds (Mn 1 − x Ni x ) 65 Ga 35 of Ni 2 In type structure are found in the range of 0.15 ⩽ x ⩽ 0.45. In the higher x range, the magnetization—temperature curves show Curie—Weiss type behaviors, but those with x ⩽ 0.35 suggest another type ferromagnet. The magnetic ordering temperature T c decreases for x ⩽ 0.2 and then increases with increasing x . The curves of 0.25 ⩽ x ⩽ 0.3 show a hump and then slightly decrease with decreasing temperature. In the neutron diffraction experiment for x = 0.275, the (0 0 1) reflection appears for 165 K ⩽ T T C to 8.47 C with temperature.

Metamagnetic transition in Y2Cu2O5

Abstract Neutron diffraction experiment has been performed to determine the magnetic structures in magnetic fields up to 6 T on a single crystal of Y 2 Cu 2 O 5 which shows strange metamagnetic transitions at H c1 = 3.0T and H c2 = 4.8T for H‖b . At H = 0, the determined magnetic structure is identical with that obtained for the powder sample, but new diffraction peaks appear at completely unexpected positions between H c1 and H c2 , which means a three-lattice period modulation along the b -axis but this structure change is mysterious from the crystallographic point of view.

Recent development of basic magnetism in interstitially modified rare-earth iron nitrides R2Fe17N3

EPMA-line profiles for N-element in Sm2Fe17Nx indicate that under low N2-gas pressure, nitrogen absorption into grain interior is mainly due to diffusion of nitrogen atoms, while under high N2-gas pressure, the grain growth of fully nitrogenated phase Sm2Fe17N3 becomes more dominant than diffusion, making high-pressure nitrogenation effective for fabricating a high-quality nitride. Neutron diffraction studies of Y2Fe17 and Y2Fe17N3.1 prepared by high N2-gas pressure revealed that the N-atoms fully occupy at the 9e-sites (99.5%) and a small amount of N-atoms locates on the 18g-sites (4%). The introduction of N-atoms into Y2Fe17 led to such a strong modification in the Fe magnetic moment that the moment of the 18f-Fe atoms being the nearest to the 9e-N atoms is the smallest (∼2.0μB), whereas the 6c-Fe atoms being the farthest from the 9e-N atoms have the largest moment of ∼2.9μB at 10 K. The magnetization measurements of Nd2Fe17N3 single crystal clarified a strong enhancement of crystalline electric field (CEF) acting on R-atoms upon nitrogenation, leading to almost three times larger CEF-parameter A20 in nitride than in host compound.

High-field magnetization on interstitially modified single crystals Nd2Fe17Z3 (Z H and N)

Abstract High-field magnetization process of Nd 2 Fe 17 single crystal and interstitially modified single crystals Nd 2 Fe 17 H 3 and Nd 2 Fe 17 N 3 at 4.2 K has been investigated to clarify the influence of interstitial H or N on basic magnetism. The second-order crystal electric field (CEF) coefficient A 2 0 was estimated on a basis of the single-ion Hamiltonian, the value of which reaches up to − 1500 K/ a 0 2 at 4.2 K upon nitrogenation and is about three times larger than that for Nd 2 Fe 17 .

Effects of decomposition on the magnetic property of shock-consolidated Sm2Fe17Nx bulk magnets

It had been found that fully dense Sm2Fe17Nx bulk bodies can be prepared by shock compression in a certain low pressure region, using the magnetically aligned powder pellets and without binder. In this study, the correlations between the shock condition, the crystal chemical state and magnetic property of the shock-consolidated bulk bodies were investigated by means of X-ray diffraction (XRD) analysis, chemical analysis and magnetic measurement. It was found that the maximum energy products decreased a great deal when the driving shock pressure (using a copper standard capsule) exceeded about 15–16 GPa. In these driving pressures, the coercivity simultaneously decreased with an appearance of Fe due to decomposition, while the decrease in remanent magnetization was almost constant. If we chose the suitable shock conditions, the decrease rate of maximum energy product from the starting material could be suppressed to less than 20–30%.

Magnetoresistance measurements of FexCo1-xSi

Abstract We performed magnetoresistance measurements of Fe 0.2 Co 0.8 Si and CoSi single crystals in the temperature range 4.2–60 K under magnetic fields up to 14 T. The transeverse and longitudinal magnetoresistance of Fe 0.2 Co 0.8 Si show the same magnetic field dependence, while the transverse magnetoresistance of CoSi is quite larger than the longitudinal one at the same magnetic field. These results are discussed in connection with their magnetic properties.

Magnetoresistance and magnetization measurements in magnetically ordered GdNiSn

Magnetoresistance of ordered crystal GdNiSn has been observed and tried to analyze by the use of magnetization data. No clear effect on the magnetization data is found at the phase-transition fields. But the magnetoresistance and differential magnetization data show the clear change made by the field-induced phase transition. Besides the important role of the spin stability on the resistance, the residual resisivity can have a different values on each phase because of the different matrix elements between its collective and nonmagnetic impurity states.

Magnetoresistance measurements of FeSi under high magnetic field

Abstract We have performed the magnetoresistance measurements of two single crystals of FeSi in the temperature range 4.2–300 K. At 4.2 K the negative magnetoresistance is observed in sample K, which has less impurities judging from its resistivity, while the magnetoresistance of sample Y shows monotonical increase. The comparison of these two samples is discussed.