H. Hiroyoshi

Spin-glass-like behavior in a Fe-Zr amorphous alloy

The thermomagnetization curves and the hyteresis loops of the amorphous alloy Fe92Zr8 at low temperature have been investigated. Spin-glass-like behavior such as a thermomagnetic history and relaxation of remanence has been observed.

Mictomagnetism of Fe-rich Fe-Zr amorphous alloys studied by AC susceptibility in a superposed DC field

The temperature dependence of the AC susceptibility Fe-rich Fe-Zr amorphous alloys having mictomagnetic or spin-glasslike behaviour has been measured in a superposed DC field. The Fe-Zr amorphous alloys containing more than 8.6 at.% Zr clearly show sharp peaks at the Curie temperature TC and the spin cluster freezing temperature Tsf. These two temperatures seem to coincide at a critical concentration for the Fe-7.6 at.% Zr alloy, which is considered to be the percolation limit for the long-range ferromagnetic interactions.

Invar effects on some iron-base amorphous alloys

Abstract The thermal expansion and magnetic properties of Fe-B and Fe-P amorphous alloys prepared from melts have been investigated. These amorphous alloys show distinct Invar characteristics. heir magnetic properties are also very similar to those of Fe-Ni crystalline Invar alloys; that is, the high-field susceptability and forced-volume magnetostriction are remarkably large, the magnetic moment per Fe atom does not increase linearly, the Curie temperature decreases with a decrease in concentration of B or P, and their reduced their magnetization curves are much flatter than those of crystalline pure Fe.

Magnetic moment and high-field susceptibility of amorphous FeB Invar-type alloys

Abstract The saturation magnetization and high-field susceptibility of amorphous Fe 100− x B x (11 ⩽ x ⩽ 22) alloys have been measured at 4.2 K, 77 K and room temperature in magnetic fields up to 100 kOe. The concentration dependence of the saturation moment per iron atom shows a maximum around 14% boron, while the high-field susceptibility increases remarkably with decreasing boron content. The features are similar to those of crystalline FeNi Invar alloys.

Metamagnetic Phase Transitions in FeTiO3

Magnetic susceptibilities and magnetization isotherms have been measured for single crystal FeTiO 3 . The susceptibility parallcl to the c -axis has a large and sharp peak at T N =58.0±0.3 K, while the perpendicular susceptibility is almost independent of temperature below T N . Magnetization isotherm at 4.2 K with fields applied along the c -axis exhibits a typical metamagnetic transition at H c =80.3±0.1 kOe, being the first observation of metamagnetism in 3 d transition metal oxides. The transition is of the first order up to about 35 K, above which it is of the second order. The experimental data are well reproduced by molecular field calculations with the best fit parameters of the anisotropy field H A =150 kOe, the ferromagnetic intrasublattice exchange interaction of 2 z 1 J 1 =28.5 K, and the antiferromagnetic intersublattice interaction of 2 z 2 J 2 =-6.67 K.

First order magnetization process in Pr2Fe14B single crystal

Abstract High-field magnetization process in Pr 2 Fe 14 B single crystal has been studied in static magnetic fields up to 230 kOe. The spontaneous magnetization is along the [001] direction of the tetragonal structure down to 1.5 K. When the field is applied along the [100] and [110] directions at low temperatures, magnetization jumps are observed at about 130 kOe and 160 kOe, respectively, which are considered to correspond to the first order magnetization process (FOMP). Observed features of the magnetization curves including FOMP and their temperature dependence are well reproduced by the calculation based on a simplified Hamiltonian including the crystalline electric fields and the FePr

Magnetic anisotropy of Sm2Fe14B single crystal

Abstract Magnetization measurements have been made on a Sm 2 Fe 14 B single crystal in magnetic fields up to 140 kOe. The easy direction of the magnetization lies along [100] in the tetragonal structure P4 2 /mnm. Magnetic anisotropy energies at 290K along [110] and [001] have been estimated to be 5.8×10 6 and 1.1×10 8 erg/cm 3 , respectively, both becoming much larger at lower temperature. No evidence of the spin canting of Nd 2 Fe 14 B type is observed even at 4.2K.

High-field magnetization of R2Fe14B single crystals

Abstract Magnetizations of R 2 Fe 14 B single crystals (R = Ce, Pr, Dy and Tm) have been measured in steady fields up to 145 kOe and in pulsed fields up to 400 kOe. The emphasis is laid on the anisotropy of apparent saturation magnetization and the incipient stage of ferri- to ferro-magnetic transition in Tm 2 Fe 14 B.

Magnetic properties of a new permanent magnet based on Nd-Fe-B compound II. Magnetization

Abstract A new permanent magnet Nd 15 Fe 77 B 8 (NEOMAX) and its basic compound Nd 2 Fe 14 B have been studied by static magnetization measurements. The average magnetic moment of the Nd ions is estimated to be 2.8μ B at 4.2 K and 2.0μ B at 290 K by subtracting the contribution of the Fe magnetic moments (2.8μ B at 4.2 K and 2.02μ B at 290 K) from the saturation moment per unit formula. The deviation of the magnetic easy axis from the c -axis, which is the easy axis at room temperature, is found below 200 K and an angle of spin canting from the c -axis is found to be ca. 20° at 77 K. By the measurement under high magnetic fields, the anisotropy constants are obtained to be k 1 = -6.0 and k 2 = 13 at 77 K, and k 1 = 4.9 and k 2 = 0.1 at 290 K in 10 7 erg/cm 3 units, respectively.

Spin flopping in MnTiO3

Abstract Susceptibility and magnetization have been measured on a single crystal of MnTiO3. Spin-flopping is observed in the magnetization curve with the field along the hexagonal c-axis. The exchange parameter and the anisotropy constant are estimated from the experimental data, the latter being 2.3 times smaller than the calculated value for the dipole interactions.