Finite-temperature magnetism of FeRh compounds

Polesya, S.; Mankovsky, S.; Ködderitzsch, D.; Minář, J.; Ebert, H.

doi:10.1103/physrevb.93.024423

Cited by 39 publications

(39 citation statements)

References 41 publications

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“…In addition, a premartensitic instability is anticipated in B2 AFM state with known phonon instabilities [57][58][59] , and a martensitic transformation from B2 AFM austenite to orthorhombic AFM martensite at cryogenic T was suggested by direct GSS-NEB calculations. 61…”

Section: Compression and Expansionmentioning

confidence: 96%

“…14 Properties of FeRh were extensively studied experimentally [12][13][14][19][20][21] and theoretically. 22,[47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] Notably, the metamagnetic T c of FeRh is sensitive to stoichiometry, lowering precipitously with small additions of at.%Rh. 29 A giant caloric effect is found at this transition in the quenched Fe 49 Rh 51 sample, 19 i.e., a directly measured temperature drop of 12.9 K at 1.95 Tesla.…”

Section: Introductionmentioning

confidence: 99%

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Reliable thermodynamic estimators for screening caloric materials

Zarkevich

Johnson

2019

Journal of Alloys and Compounds

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Reversible, diffusionless, first-order solid-solid phase transitions accompanied by caloric effects are critical for applications in the solid-state cooling and heat-pumping devices. Accelerated discovery of caloric materials requires reliable but faster estimators for predictions and high-throughput screening of system-specific dominant caloric contributions. We assess reliability of the computational methods that provide thermodynamic properties in relevant solid phases at or near a phase transition. We test the methods using the well-studied B2 FeRh alloy as a "fruit fly" in such a materials genome discovery, as it exhibits a metamagnetic transition which generates multicaloric (magneto-, elasto-, and baro-caloric) responses. For lattice entropy contributions, we find that the commonly-used linear-response and smalldisplacement phonon methods are invalid near instabilities that arise from the anharmonicity of atomic potentials, and we offer a more reliable and precise method for calculating lattice entropy at a fixed temperature. Then, we apply a set of reliable methods and estimators to the metamagnetic transition in FeRh (predicted 346 ± 12 K, observed 353 ± 1 K) and calculate the associated caloric properties, such as isothermal entropy and isentropic temperature changes.

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Section: Compression and Expansionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Reliable thermodynamic estimators for screening caloric materials

Zarkevich

Johnson

2019

Journal of Alloys and Compounds

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“…Previous first‐principles studies concentrated on the electronic part and total energy due to magnetic excitations . Encouraged by the good agreement of the Fe‐projected VDOS between experiment and theory in both phases of FeRh, we therefore attempted a similar approach to that presented for La–Fe–Si in Section 2.1.…”

Section: Disentangling the Microscopic Contributions To The Entropy Cmentioning

confidence: 99%

Hysteresis Design of Magnetocaloric Materials—From Basic Mechanisms to Applications

et al. 2018

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Magnetic refrigeration relies on a substantial entropy change in a magnetocaloric material when a magnetic field is applied. Such entropy changes are present at first‐order magnetostructural transitions around a specific temperature at which the applied magnetic field induces a magnetostructural phase transition and causes a conventional or inverse magnetocaloric effect (MCE). First‐order magnetostructural transitions show large effects, but involve transitional hysteresis, which is a loss source that hinders the reversibility of the adiabatic temperature change ΔTad. However, reversibility is required for the efficient operation of the heat pump. Thus, it is the mastering of that hysteresis that is the key challenge to advance magnetocaloric materials. We review the origin of the large MCE and of the hysteresis in the most promising first‐order magnetocaloric materials such as Ni–Mn‐based Heusler alloys, FeRh, La(FeSi)13‐based compounds, Mn3GaC antiperovskites, and Fe2P compounds. We discuss the microscopic contributions of the entropy change, the magnetic interactions, the effect of hysteresis on the reversible MCE, and the size‐ and time‐dependence of the MCE at magnetostructural transitions.

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“…They were able to reproduce a transition from AF to FM, albeit at a rather large temperature and atomic volume. In a similar spirit, Polesya et al evaluated an extended Heisenberg Hamiltonian which only acts on the Fe atoms, where the FM exchange interaction is scaled according to a response function dependent on the Rh moments [54]. With magnetic exchange parameters self-consistently obtained from uncompensated DLM calculations, which correspond to the average moment of the configuration, they obtain a very reasonable transition temperature of ∼320 K.…”

Section: Published By the American Physical Society Under The Terms Omentioning

confidence: 99%

Impact of lattice dynamics on the phase stability of metamagnetic FeRh: Bulk and thin films

et al. 2016

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We present phonon dispersions, element-resolved vibrational density of states (VDOS) and corresponding thermodynamic properties obtained by a combination of density functional theory (DFT) and nuclear resonant inelastic x-ray scattering (NRIXS) across the metamagnetic transition of B2 FeRh in the bulk material and thin epitaxial films. We see distinct differences in the VDOS of the antiferromagnetic (AF) and ferromagnetic (FM) phases, which provide a microscopic proof of strong spin-phonon coupling in FeRh. The FM VDOS exhibits a particular sensitivity to the slight tetragonal distortions present in epitaxial films, which is not encountered in the AF phase. This results in a notable change in lattice entropy, which is important for the comparison between thin film and bulk results. Our calculations confirm the recently reported lattice instability in the AF phase. The imaginary frequencies at the X point depend critically on the Fe magnetic moment and atomic volume. Analyzing these nonvibrational modes leads to the discovery of a stable monoclinic ground-state structure, which is robustly predicted from DFT but not verified in our thin film experiments. Specific heat, entropy, and free energy calculated within the quasiharmonic approximation suggest that the new phase is possibly suppressed because of its relatively smaller lattice entropy. In the bulk phase, lattice vibrations contribute with the same sign and in similar magnitude to the isostructural AF-FM phase transition as excitations of the electronic and magnetic subsystems demonstrating that lattice degrees of freedom need to be included in thermodynamic modeling.

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Finite-temperature magnetism of FeRh compounds

Cited by 39 publications

References 41 publications

Reliable thermodynamic estimators for screening caloric materials

Reliable thermodynamic estimators for screening caloric materials

Hysteresis Design of Magnetocaloric Materials—From Basic Mechanisms to Applications

Impact of lattice dynamics on the phase stability of metamagnetic FeRh: Bulk and thin films

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