### Abstract

The Néel temperature TN, electronic specific heat coefficient γ_{e}, band structures and the effective exchange constant J_{0} of the L1_{0}-type MnIr alloy system have been investigated. The value of T_{N} 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 T_{N} and the experimental electronic specific heat coefficient γ_{e} is small of 2-3mJmol^{-1}K^{-2}, characteristic to pseudo-gap-type antiferromagnets, though γ_{e} is rather larger than that of other L1_{0}-type Mn alloy systems. In addition, the concentration dependences of TN and γ_{e} 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^{-1}atom^{-1}spin^{-1}, corresponding to about 1mJmol^{-1}K^{-2} of the calculated electronic specific heat coefficient γcale. The Néel temperature TcalN calculated from J_{0} in the molecular field approximation is 1495 K, highest among several kinds of the L1_{0}-type equiatomic Mn alloy systems. From the calculated results of T^{cal}_{N} under the different additive element and/or the lattice constants, it is concluded that the magnitude of the Néel temperature TN of the L1_{0}-type equiatomic Mn alloy systems is explained by the J_{0} curve which reflects the difference in the number of electrons at the Mn site.

Original language | English |
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Journal | Physical Review B - Condensed Matter and Materials Physics |

Volume | 69 |

Issue number | 10 |

DOIs | |

Publication status | Published - 2004 Mar 17 |

### ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics