H. Yamada

Electronic structure and magnetic properties of YM2 compounds (M=Mn, Fe, Co and Ni)

The electronic structures of itinerant de electrons in the intermetallic compounds YMn2, YFe2, YCo2 and YNi2 with cubic Laves-phase structure are calculated using both the recursion method and the standard method of the tight-binding approximation (TBA). Using the calculated density-of-states curves in the TBA and taking the effect of spin fluctuations into account, the temperature dependences of the paramagnetic spin susceptibility in these compounds are calculated. The field dependence of the induced magnetic moment in YCo2 at OK is also calculated. Good agreement between the calculated and observed results can be obtained by allowing the number of d electrons to be an adjustable parameter. Furthermore, the densities of states for magnetised YCo2 and ferromagnetic YFe2 are calculated. It is shown that the values of the local magnetic moments on Co and Fe are smaller than those in pure metals and the local magnetic moments on Y become negative due to the hybridisation between the d bands of Y and Co or Fe.

Electronic structure and magnetic properties of the cubic Laves phase compounds ACo2 (A=Sc, Ti, Zr, Lu and Hf) and ScNi2

Electronic structures of d electrons in the intermetallic compounds ScCo2, TiCo2, ZrCo2, LuCo2, HfCo2 and ScNi2 with cubic Laves phase structure are calculated in the tight-binding approximation. By using the calculated density-of-states curves and taking the effect of spin fluctuations into account, the temperature dependences of the paramagnetic spin susceptibility in these compounds are calculated. The magnetic field dependence of the induced magnetic moment in LuCo2 at 0K is also calculated. Good agreement between the calculated and observed results is obtained. As observed in ZrCo2 and HfCo2, moreover, an excess Co atom in the Co-rich non-stoichiometric compounds is shown to have a local magnetic moment.

Electronic structure and magnetic properties of the cubic Laves phase compounds AFe2 (A=Zr, Lu and Hf)

The electronic structures of d electrons in the cubic Laves phase of the intermetallic compounds ZrFe2, LuFe2 and HfFe2 are calculated by the right-binding approximation both in the paramagnetic and ferromagnetic states. By using the density-of-states curve in the paramagnetic state and taking into account the effect of spin fluctuations, the temperature dependence of the paramagnetic spin susceptibility is calculated. For ZrFe2 a good agreement between the calculated and observed results is obtained. In the ferromagnetic state, the local moments of Zr, Lu, Hf and Fe atoms are calculated and it is shown that the local moments on Zr, Lu and Hf atoms are antiparallel to those on Fe atoms. Moreover, the high-field spin susceptibility is estimated. A brief discussion on the anomalously large magnetic moment observed in the ZrFe2 hydrides is given.

Metamagnetic transition of YCo2

The electronic structure of d electrons in the cubic Laves phase of the intermetallic compound YCo2 under an external magnetic field is calculated in the tight-binding approximation. The magnetic-field dependence of the induced moment is obtained at 0K and it is shown that the metamagnetic transition from the paramagnetic to ferromagnetic state occurs at about 90 T. It is also shown that the different hybridisations between the 3d band of Co and the 4d band of Y or the 5d band of R (where R is a rare earth) with majority and minority spins play an important role in the appearance of the local moment on Co in the magnetised state of the compounds YCo2 or RCo2.

Electronic structure of the ordered ternary compound Y(M0.75Al0.25)2 (M=Co and Fe) with C15-type Laves phase structure

Abstract The electronic structures of the binary compound YM 2 and the ordered ternary compound Y(M 0.75 Al 0.25 ) 2 (M = Co and Fe) with the C15-type Laves phase structure are calculated by the self-consistent APW method. It is shown that the calculated density-of-states (DOS) curves for YM 2 are very similar to those obtained previously, being characterised by two sharp peaks mainly of 3d-states of M atoms near the Fermi level. For ordered Y(M 0.75 Al 0.25 ) 2 , some 3d-states of the M atom hybridise strongly with 3p-states of the Al atom and only a single sharp peak is shown to appear in the DOS near the Fermi level. Moreover, the position of the Fermi level is shown to shift toward the lower energy side by the substitution of Al atoms. The anomalous magnetic properties observed in the pseudobinary compound Y(M,Al) 2 are discussed on the basis of these calculated electronic structures.

Pressure effect in an itinerant-electron metamagnet at finite temperature

Abstract Taking the effect of spin fluctuations into account, the pressure effect on the metamagnetic transition (MT) in an itinerant-electron system is discussed at finite temperature. A characteristic relation between two phenomena, the susceptibility maximum and the MT, is also discussed under the pressure. It is shown that the MT disappears at a certain pressure. The critical pressure of the MT is shown to decrease with increasing temperature and becomes zero at a critical temperature. The pressure dependence of the critical temperature, at which the MT disappears, is obtained. Numerical calculations are carried out for an actual itinerant-electron metamagnet YCo 2 .

The itinerant electron metamagnetism for ScCo2, YCo2 and LuCo2

Abstract Electronic structure of d-electrons under external magnetic field is calculated for ScCo 2 , YCo 2 and LuCo 2 in the self-consistent tight-binding approximation and the field dependence of the induced moment is estimated in the Hartree-Fock approximation. The critical field of the metamegnetic transition for these compounds is evaluated at 0 K.

Electronic structure and magnetic properties of antiferromagnetic YMn2

The electronic structure of d electrons in the antiferromagnetic intermetallic compound YMn2 with the cubic Laves phase structure is calculated in the tight-binding approximation. In the Hartree-Fock approximation, the density of states curve and the sublattice moment of Mn atoms are calculated numerically at 0 K. It is shown that the magnitude of the sublattice Mn moment decreases with decreasing lattice constant. Furthermore, the parallel and perpendicular spin susceptibilities are calculated numerically at 0 K and it is shown that the perpendicular spin susceptibility is much larger than the parallel one. A discussion on the magnetic structure of GdMn2 is given.

Metamagnetic transition of ScCo2 and LuCo2

The electronic structure of d electrons in the cubic Laves phase of the intermetallic compounds ScCo2 and LuCo2 under an external magnetic field is calculated in the tight-binding approximation and in the Hartree-Fock approximation. The field dependence of the induced moment is obtained at 0K. It is shown that the metamagnetic transition from the paramagnetic to the ferromagnetic state can occur at about 120 and 94 T for ScCo2 and LuCo2, respectively.

Magnetic properties of Zr(Fe-Co)2

Abstract The electronic structure of the d-electrons in the pseudo-binary compound Zr(Fe, Co) 2 is calculated with the tight-binding method and virtual crystal approximation. From the comparison between the calculated and observed results of the concentration dependence of the magnetization it is concluded that two magnetic regions with large moment and without moment coexist near the critical concentration of the onset of magnetization.