Temperature-dependent transport properties of FeRh

Abstract

The finite-temperature transport properties of FeRh compounds are investigated by first-principles Density Functional Theory-based calculations. The focus is on the behavior of the longitudinal resistivity with rising temperature, which exhibits an abrupt decrease at the metamagnetic transition point, T = Tm between ferro-and antiferromagnetic phases. A detailed electronic structure investigation for T ≥ 0 K explains this feature and demonstrates the important role of (i) the difference of the electronic structure at the Fermi level between the two magnetically ordered states and (ii) the different degree of thermally induced magnetic disorder in the vicinity of Tm, giving different contributions to the resistivity. To support these conclusions, we also describe the temperature dependence of the spin-orbit induced anomalous Hall resistivity and Gilbert damping parameter. For the various response quantities considered the impact of thermal lattice vibrations and spin fluctuations on their temperature dependence is investigated in detail. Comparison with corresponding experimental data finds in general a very good agreement. PACS numbers: Valid PACS appear hereFor a long time the ordered equiatomic FeRh alloy has attracted much attention owing to its intriguing temperature dependent magnetic and magnetotransport properties. The crux of these features of this CsCl-structured material is the first order transition from an antiferromagnetic (AFM) to ferromagnetic (FM) state when the temperature is increased above T m = 320 K [1,2]. In this context the drop of the electrical resistivity that is observed across the metamagnetic transition is of central interest. Furthermore, if the AFM to FM transition is induced by an applied magnetic field, a pronounced magnetoresistance (MR) effect is found experimentally with a measured MR ratio ∼ 50% at room temperature [2][3][4]. The temperature of the metamagnetic transition as well as the MR ratio can be tuned by addition of small amounts of impurities [2,[5][6][7][8]. These properties make FeRh-based materials very attractive for future applications in data storage devices. The origin of the large MR effect in FeRh, however, is still under debate. Suzuki et al. [9] suggest that, for deposited thin FeRh films, the main mechanism stems from the spin-dependent scattering of conducting electrons on localized magnetic moments associated with partially occupied electronic dstates [10] at grain boundaries. Kobayashi et al. [11] have also discussed the MR effect in the bulk ordered FeRh system attributing its origin to the modification of the Fermi surface across the metamagnetic transition. So far only one theoretical investigation of the MR effect in FeRh has been carried out on an ab-initio level [12].The present study is based on spin-polarized, electronic structure calculations using the fully relativistic multiple scattering KKR (Korringa-Kohn-Rostoker) Green function method [13][14][15]. This approach allowed to calculate the transport properties of FeRh at finite temperature...

Spin pumping during the antiferromagnetic–ferromagnetic phase transition of iron–rhodium

“…6d. As calculated, the intrinsic damping α Gilbert increases from 0.0024 to 0.0031 bỹ 29.2%, in good agreement with the values reported previously 30 .…”

“…The T-dependent magnetization loops clearly demonstrate the phase transition between AFM and FM-FeRh, where the transition temperatures locate between 300 and 380 K for different samples. Since the AFM and FM states of FeRh contribute differently to the transport properties, an abrupt change in resistance is observed during the phase transition 30,33 .…”

“…It is worth emphasizing that the slight increase of α Gilbert is consistent with the experimental resistance change during the phase transition. For a common FM, the damping will increase towards high (low) temperature as a consequence of interband (intraband) scattering, which is called resistivity-like (conductivity-like) behavior 30 . Specifically, for the case of FeRh where the phase transition occurs above 300 K, interband scattering is expected to dominate and the Gilbert damping α Gilbert (T) is generally proportional to the electrical resistivity ρ (ref.…”

“…Specifically, for the case of FeRh where the phase transition occurs above 300 K, interband scattering is expected to dominate and the Gilbert damping α Gilbert (T) is generally proportional to the electrical resistivity ρ (ref. 30 ). So α Gilbert (T) is expected to increase by 28.9% during the phase transition, which is consistent with the derived result based on K ?…”

“…The crucial role of AFM-FeRh as a spin detector is further confirmed by vertical spin pumping experiments from Py into FeRh. In addition to the low damping of~0.0023 in the FM state which makes it competitive for magnonic and spin-orbitronic applications 30 , the greatly enhanced damping related to the AFM phase during the phase transition opens prospects towards ultrafast logic devices. The observation of lateral spin pumping and modulated damping are fundamentally significant for understanding the spin dynamics in FeRh and might advance its practical application in AFM spintronics.…”