Electrical and Magnetic Properties, and Electronic Structures of Pseudo-Gap-Type Antiferromagnetic <I>L</I>1<SUB>0</SUB>-Type MnPt Alloys

Abstract

The electrical resistivity &, magnetic susceptibility 1, electronic specific heat coefficient e , the Néel temperature T N and the electronic structure and the magnetocrystalline anisotropy energy (MAE) have been investigated for L1 0 -type MnPt alloy system. This alloy system exhibits the characteristic behaviors of pseudo-gap type antiferromagnets, presenting with the highest T N , the smallest values of &, 1 and e in the vicinity of the equiatomic composition. The values of &, 1 and e increase with deviating from the equiatomic composition.From the linear muffin-tin orbital (LMTO) band calculations, the L1 0 -type MnPt alloy system has a pseudo-gap in the electronic structure and the density of states (DOS) at the Fermi energy (E F ) is lowest at the equiatomic composition in accord with the experimental results. Furthermore, the results of the LMTO band calculations including the spin-orbit interaction make it clear that the direction of the magnetic moment of Mn in the equiatomic composition is parallel to the c-axis, consistent with the reported spin structure determined by neutron diffractions. The magnetocrystalline anisotropy constant K is about 1:39 Â 10 6 J m À3 which is larger in magnitude than that of L1 0 -type MnNi equiatomic alloy, though the signs are different.

Evidence of Change in the Density of States during the Martensitic Phase Transformation of Ni-Mn-In Metamagnetic Shape Memory Alloys

“…The obtained results may provide indirect information on the electronic state, in contrast to the photoelectron spectroscopy observations that provide direct information. However, it has been reported that the value of γ for L1 0 -type NiMn alloy and related materials (i.e., PdMn and PtMn) where the existence of the pseudo-gap around E F characterizes their unique electronic states agrees well with the value obtained by theoretical calculations [11][12][13]. Systematic study of the specific heat measurements in a wide composition region for Ni-Mn-In will help understand the behavior of the metamagnetic shape memory alloys in this system.…”

Crystal and magnetic structure of antiferromagnetic Mn2PtPd

“…It is noted that we did not observe any significant change in the magnetic configuration below 470 K which indicates that the irreversibility in the M(T) curve (figure 2a) is rather related to off-stoichiometry or defects than being an intrinsic bulk property. 8 The determined moment value at 296 K is μexp(Mn) = 4.09(10) μB, which is similar as for many other magnetic intermetallic alloys containing Mn [24][25][26]29,31,37]. The temperature dependence of the magnetic moment of the Mn atom was investigated in the temperature range from 296 to 1012 K. In figure 4(a) it is seen that the saturation of the magnetic moments is almost reached at 296 K. The magnetic order disappears at the Néel temperature TN = 866 (5) K. The lattice parameters, the c/a ratio, and the volume of the unit cell are displayed in figure 4 (b) and 4 (c) respectively.…”

“…MnPt alloys due to a very small deviation from the equiatomic composition [26]. Therefore, a small amount of off-stoichiometry in the sample could be the reason for this kind of behaviour and also for the irreversibility in the magnetization being observed at 470 K on cooling (figure 2(a)).…”

Magnetic anisotropy energy of antiferromagnetic L1-type equiatomic Mn alloys

“…1, the MAE of the MnPt alloy shows a positive value, indicating that the magnetic moment of Mn is parallel to the c axis in the L1 0 -type structure. 27 The calculated results using the same procedure are illustrated in Fig. 2 Furthermore, we should not overlook that the variation of the MAE against q for the MnPt alloy is more sensitive than that of the MnNi and MnPd alloys in Fig.…”