Magnetic exchange interactions and critical temperature of the nanolaminate Mn2GaC from first-principles supercell methods
2016 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 93, no 5Article in journal (Refereed) Published
In this work, we employ and critically evaluate a first-principles approach based on supercell calculations for predicting the magnetic critical order-disorder temperature 𝑇𝑐 . As a model material we use the recently discovered nanolaminate Mn2GaC.
First, we derive the exchange interaction parameters 𝐽𝑖𝑗 between pairs of Mn atoms on sites 𝑖 and 𝑗 of the bilinear Heisenberg Hamiltonian using the novel magnetic direct cluster averaging method (MDCA), and then compare the 𝐽’s from the MDCA calculations to the same parameters calculated using the Connolly-Williams method. We show that the two methods yield closely matching results, but observe that the MDCA method is computationally less effective when applied to highly ordered phases such as Mn2GaC.
Secondly, Monte Carlo simulations are used to derive the magnetic energy, specific heat, and 𝑇𝑐 . For Mn2GaC, we find 𝑇𝑐 = 660 K. The uncertainty in the calculated 𝑇𝑐 caused by possible uncertainties in the 𝐽’s is discussed and exemplified in our case by an analysis of the impact of the statistical uncertainties of the MDCA-derived 𝐽’s, resulting in a 𝑇𝑐 distribution with a standard deviation of 133 K.
Place, publisher, year, edition, pages
2016. Vol. 93, no 5
IdentifiersURN: urn:nbn:se:liu:diva-124563DOI: 10.1103/PhysRevB.93.054432ISI: 000371391800004OAI: oai:DiVA.org:liu-124563DiVA: diva2:900114
Funding agencies: European Research Council under the European Community Seventh Framework Program (FP7)/ERC Grant ; Swedish Research Council (VR) [621-2011-4417, 330-2014-6336]; Knut and Alice Wallenberg (KAW) Fellowship program; SSF synergy grant FUNCASE2016-02-032016-02-032016-04-07Bibliographically approved