Antiferromagnetic-ferromagnetic transition in FeRh

Moruzzi, V. L.; Marcus, P. M.

doi:10.1103/physrevb.46.2864

Cited by 175 publications

(138 citation statements)

References 19 publications

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“…close to the theoretical and experimental equilibrium volume. 18 For each of the atoms the spin-up and spin-down DOS clearly differ, resulting in large atomic magnetic moments: 3.11 μ B for Fe and 1.07 μ B for Rh. The comparison of the Fe and Rh DOS corresponding to the same spin projection shows that they have a common peak structure.…”

Section: Nature Of Rh Momentmentioning

confidence: 99%

Magnetic excitations and femtomagnetism of FeRh: A first-principles study

2011

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The paper is partly motivated by recent pump-probe experiments with ultrashort laser pulses on antiferromagnetic FeRh that have shown the generation of magnetization within a subpicosecond time scale. On the other hand, the physical mechanism of the thermal antiferromagnetic-ferromagnetic (AFM-FM) phase transition in FeRh, known for many decades, remains a topic of controversial discussions. The selection of the magnetic degrees of freedom as well as the treatment of the magnetic excited states differ strongly in recent models by different authors. We report a density functional theory (DFT) investigation of FeRh. For the study of excited states, DFT calculations with constraints imposed on the directions and values of the atomic moments are employed. We show that the formation of the Rh moment as a consequence of the AFM-FM phase transition cannot be described within the Stoner picture. Instead, an implicit spin splitting of the Rh states takes place in the AFM phase, resulting in the intra-atomic spin polarization of the Rh atoms. This property is a consequence of the strong hybridization between Rh and Fe states. The Fe-Rh hybridization is an important factor in the physics of FeRh. We demonstrate that the ferromagnetic Fe-Rh exchange interaction is robust with respect to the crystal volume variation, whereas the antiferromagnetic Fe-Fe exchange interaction is strongly volume dependent. These different volume dependencies of the competing exchange interactions lead to their strong compensation at certain crystal volume. We perform Monte Carlo simulations and show that the calculated thermodynamics depends on the way the magnetic degrees of freedom are selected. We argue that the excited states resulting from the variation of the value of the Rh moment treated as degree of freedom are important for both the equilibrium thermodynamics of FeRh and the femtomagnetic phenomena in this system. We also study the spin mixing caused by spin-orbit coupling. The obtained value of the Elliott-Yafet spin-mixing parameter is comparable with earlier calculations for the ferromagnetic 3d metals. We draw the conclusion that the Elliott-Yafet mechanism of the angular-momentum transfer between electrons and lattice plays an important role in the femtomagnetic properties of FeRh.

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Section: Nature Of Rh Momentmentioning

confidence: 99%

Magnetic excitations and femtomagnetism of FeRh: A first-principles study

2011

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“…Several investigations into electronic and magnetic structures using various band-structure calculation methods have been reported to date. 21 …”

Section: Introductionmentioning

confidence: 99%

Theoretical Investigation on Electronic and Magnetic Structures of FeRh

et al. 2016

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In order to clarify the mechanism behind antiferromagnetic (AFM)-ferromagnetic (FM) phase transition, we investigate the electronic and magnetic structures of FeRh by using first principles calculations with the GGA + U method. By choosing the appropriate values of the on-site Coulomb interaction (U) of Fe3d and Rh4d electrons, we succeed in explaining the reported AFM-FM phase transition experiments for the first time by obtaining the total energy difference between the AFM and FM states (ΔE). Other physical quantities such as the density of states (DOS) are also consistent with experimental reports.

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“…Although these examples (as a direct consequence of mixed-phase coexistence) all occur in systems that are insulating (at least until chemically doped), we extend the same concept to metallic systems of FeRh in this report. FeRh exhibits a temperature-dependent first-order phase transition at B100°C from an AFM (low temperature) to a FM (high temperature) phase that is characterized by 1% expansion in the volume [13][14][15][16][17][18][19] . Although the origin of the phase transition has long been a subject of theoretical studies 20,21 , it is now believed to result from different temperature dependencies of the entropy in the two phases 22,23 .…”

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Large resistivity modulation in mixed-phase metallic systems

et al. 2015

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In numerous systems, giant physical responses have been discovered when two phases coexist; for example, near a phase transition. An intermetallic FeRh system undergoes a first-order antiferromagnetic to ferromagnetic transition above room temperature and shows two-phase coexistence near the transition. Here we have investigated the effect of an electric field to FeRh/PMN-PT heterostructures and report 8% change in the electrical resistivity of FeRh films. Such a 'giant' electroresistance (GER) response is striking in metallic systems, in which external electric fields are screened, and thus only weakly influence the carrier concentrations and mobilities. We show that our FeRh films comprise coexisting ferromagnetic and antiferromagnetic phases with different resistivities and the origin of the GER effect is the strain-mediated change in their relative proportions. The observed behaviour is reminiscent of colossal magnetoresistance in perovskite manganites and illustrates the role of mixed-phase coexistence in achieving large changes in physical properties with low-energy external perturbation.

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Antiferromagnetic-ferromagnetic transition in FeRh

Cited by 175 publications

References 19 publications

Magnetic excitations and femtomagnetism of FeRh: A first-principles study

Magnetic excitations and femtomagnetism of FeRh: A first-principles study

Theoretical Investigation on Electronic and Magnetic Structures of FeRh

Large resistivity modulation in mixed-phase metallic systems

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