Abstract
We present ab initio calculations of magnetic exchange parameters of stoichiometric Heusler compound NiMnSn and a few nonstoichiometric NiMnSn cases. Use of the exchange parameters in subsequent Monte Carlo simulations allows us to evaluate the magnetization curves as a function of temperature and composition as well as the critical temperatures of the magnetic phase transitions. The latter are compared to those obtained from a mean-field approximation using the Heisenberg model. We find that the variation of the experimental Curie temperatures of nonstoichiometric alloys can be explained theoretically if we assume that the main impact of disorder is the intermixing of manganese and tin on their corresponding sublattices and the simultaneous appearance of strong antiferromagnetic trends which originate from the nearest-neighbor Mn-Mn interactions on different sublattices. The Curie temperatures of the Ni-Mn-Sn alloys which have been obtained from the Monte Carlo simulations are in qualitative agreement with the experimental transition temperatures.
1 More- Received 26 April 2012
- Corrected 4 January 2013
DOI:https://doi.org/10.1103/PhysRevB.86.134418
©2012 American Physical Society
Corrections
4 January 2013