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Using pressure to tune spin reorientations in a rare earth - transition metal magnet

Tunability of the spin reorientation transitions with pressure in NdCo₅

Appl. Phys. Lett. 116, 102408 (2020); https://doi.org/10.1063/1.5135640

Santosh Kumar^a),

Christopher E. Patrick,

Rachel S. Edwards,

Geetha Balakrishnan,

Martin R. Lees^b), and

Julie B. Staunton

We present pressure-dependent magnetization measurements carried out in the domain of the spin reorientation transitions (SRTs) of a NdCo₅ single crystal. The application of a hydrostatic pressure leads to a shift in the SRTs to higher temperatures. This shift is found to be very sensitive to pressure, with the SRT temperatures increasing at a rate of

\approx 17

K/GPa. To explain the experimental results, we have also performed first-principles calculations of the SRT temperatures for different applied strains, which corroborate the experimental findings. The calculations attribute the pressure dependence of the SRTs to a faster weakening of the Co contribution to the magnetocrystalline anisotropy with pressure compared to the Nd contribution.

Fri 13 Mar 2020, 13:09

New framework provides a parameter-free approach to computational modeling of rare earth/transition metal magnets at nonzero temperature

Temperature-dependent magnetocrystalline anisotropy of rare earth/transition metal permanent magnets from first principles: The light RCo5 (R=Y, La - Gd) intermetallics

Christopher E. Patrick and Julie B. Staunton, Phys. Rev. Materials 3. 101401(R), (2019). – Published 3 October 2019 https://doi.org/10.1103/PhysRevMaterials.3.101401

This paper appears as a highlight in the latest version of Physical Review Materials as an Editor's Suggestion.

Rare earth/transition metal intermetallics remain the subject of much experimental and theoretical research due to their unrivaled performance as permanent magnets. A challenge when using electronic structure calculations to model these materials is accounting for the temperature-induced disorder of individual magnetic moments. Here, the authors combine crystal field theory with density-functional calculations to study the temperature-dependent magnetic anisotropy of the RCo $_{5}$ family of permanent magnets. The calculations reproduce the huge room temperature anisotropy of SmCo $_{5}$ and the spin reorientation transition temperatures of NdCo $_{5}$ , and highlight interesting 4 $f$ electron correlations in CeCo $_{5}$ and PrCo $_{5}$ . More generally, the developed framework provides a parameter-free approach to modeling rare earth/transition metal magnets at nonzero temperature.

Thu 03 Oct 2019, 16:36

Ab initio theory of the Gibbs free energy of itinerant electron systems: The magnetism of the Mn3A materials class

Ab initio theory of the Gibbs free energy and a hierarchy of local moment correlation functions in itinerant electron systems: The magnetism of the ${Mn}_{3} A$ materials class

Eduardo Mendive-Tapia and Julie B. Staunton, Phys. Rev. B 99, 144424 (2019) – Published 25 April 2019. https://doi.org/10.1103/PhysRevB.99.144424

Phase diagrams and the temperature and field dependence of complex magnetic materials are described here by an $a b i n i t i o$ theory. Consideration of fluctuating local degrees of freedom (‘local moments’), emerging from a material’s interacting itinerant electrons, produces naturally a picture of multisite magnetic interactions. Accurate prediction of the order of transitions and the role of both electronic and magnetoelastic effects in the Gibbs free energy coefficients are demonstrated by application to the widely varying frustrated magnetism of Mn $_{3}$ $A$ .

This paper appears as a highlight in the latest version of Physical Review B as an Editor's Suggestion.

Fri 26 Apr 2019, 09:16

Using pressure to tune spin reorientations in a rare earth - transition metal magnet

New framework provides a parameter-free approach to computational modeling of rare earth/transition metal magnets at nonzero temperature

Ab initio theory of the Gibbs free energy of itinerant electron systems: The magnetism of the Mn3A materials class

Ab initio theory of the Gibbs free energy and a hierarchy of local moment correlation functions in itinerant electron systems: The magnetism of the Mn3A materials class

Ab initio theory of the Gibbs free energy and a hierarchy of local moment correlation functions in itinerant electron systems: The magnetism of the ${Mn}_{3} A$ materials class