Pseudogap in the density of states and the highest Néel temperature of the L10-type MnIr alloy system

R. Y. Umetsu, M. Miyakawa, K. Fukamichi, A. Sakuma

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Abstract

The Néel temperature TN, electronic specific heat coefficient γe, band structures and the effective exchange constant J0 of the L10-type MnIr alloy system have been investigated. The value of TN is highest among Mn alloy systems, being 1145 K for the alloy with 50.1% Ir. The temperature dependence of electrical resistivity exhibits a hump just below TN and the experimental electronic specific heat coefficient γe is small of 2-3mJmol-1K-2, characteristic to pseudo-gap-type antiferromagnets, though γe is rather larger than that of other L10-type Mn alloy systems. In addition, the concentration dependences of TN and γe are not so sensitive to the Ir concentration. These behaviors are well explained by the theoretical calculations, that is, a pseudogap is formed around the Fermi level EF and the total density of states of the equiatomic MnIr alloy in the antiferromagnetic state is about 6 states Ry-1atom-1spin-1, corresponding to about 1mJmol-1K-2 of the calculated electronic specific heat coefficient γcale. The Néel temperature TcalN calculated from J0 in the molecular field approximation is 1495 K, highest among several kinds of the L10-type equiatomic Mn alloy systems. From the calculated results of TcalN under the different additive element and/or the lattice constants, it is concluded that the magnitude of the Néel temperature TN of the L10-type equiatomic Mn alloy systems is explained by the J0 curve which reflects the difference in the number of electrons at the Mn site.

Original languageEnglish
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume69
Issue number10
DOIs
Publication statusPublished - 2004 Mar 17

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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