Antiferromagnetism in Ru2MnZ(Z=Sn,Sb,Ge,Si) full Heusler alloys: Effects of magnetic frustration and chemical disorder

Sergii Khmelevskyi, Eszter Simon, and László Szunyogh
Phys. Rev. B 91, 094432 – Published 30 March 2015

Abstract

We present systematic theoretical investigations to explore the microscopic mechanisms leading to the formation of antiferromagnetism in Ru2MnZ(Z=Sn,Sb,Ge,Si) full Heusler alloys. Our study is based on first-principles calculations of interatomic Mn-Mn exchange interactions to set up a suitable Heisenberg spin model and on subsequent Monte Carlo simulations of the magnetic properties at finite temperature. The exchange interactions are derived from the paramagnetic state, while a realistic account of long-range chemical disorder is made in the framework of the coherent potential approximation. We find that in the case of the highly ordered alloys (Z=Sn and Sb), the exchange interactions derived from the perfectly ordered L21 structure lead to Néel temperatures in excellent agreement with the experiments, whereas, in particular in the case of Si, the consideration of chemical disorder is essential to reproduce the experimental Néel temperatures. Our numerical results suggest that by improving a heat treatment of the samples to suppress the intermixing between the Mn and Si atoms, the Néel temperature of the Si-based alloys can potentially be increased by more than 30%. Based on calculated biquadratic exchange couplings, we evidence a lifting of degeneracy of the antiferromagnetic ground states on a frustrated face-centered-cubic lattice in the fully ordered compounds. Furthermore, we show that in strongly disordered Ru2MnSi alloys, a distinct change in the antiferromagnetic ordering occurs.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Received 17 January 2015
  • Revised 13 March 2015

DOI:https://doi.org/10.1103/PhysRevB.91.094432

©2015 American Physical Society

Authors & Affiliations

Sergii Khmelevskyi1, Eszter Simon1, and László Szunyogh1,2

  • 1Department of Theoretical Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary
  • 2MTA-BME Condensed Matter Research Group, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 91, Iss. 9 — 1 March 2015

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review B

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×