Structural and magnetic properties ofHfFe6Ge6-typeErMn6Sn6−xGax(x=0–2.0)compounds

Abstract

Magnetic and structural properties of ${\mathrm{ErMn}}_{6}{\mathrm{Sn}}_{6\ensuremath{-}x}{\mathrm{Ga}}_{x}$ $(x=0\ensuremath{-}2.0)$ with the ${\mathrm{HfFe}}_{6}{\mathrm{Ge}}_{6}$-type structure have been investigated. The compounds $(x=0.2\ensuremath{-}2.0)$ are characterized by ferrimagnetic ordering, and Curie temperatures increase from 75 K for $x=0$ to 383 K for $x=0.4$ and then decrease to 288 K for $x=2.0,$ which are due to the contraction of the unit cell and the decrease of conduction-electron density with Ga substitution. The compounds $(x=0.2\ensuremath{-}2.0)$ display large coercive fields $(0.73<~{\ensuremath{\mu}}_{0i}{H}_{c}<~2.2\mathrm{T})$ at 5 K. The sign of the second-order crystalline electric-field (CEF) coefficient ${A}_{2}^{0}$ of the Er sublattice reverses by a small amount of Ga substitution for Sn. Moreover, the fourth-order CEF coefficient ${A}_{4}^{0}$ of the Er sublattice and sixth-order Stevens factor ${\ensuremath{\gamma}}_{J}$ are proved to play important roles in the determination of the easy magnetic direction.