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

Abstract

FeRh attracts intensive interest in antiferromagnetic (AFM) spintronics due to its first-order phase transition between the AFM and ferromagnetic (FM) phase, which is unique for exploring spin dynamics in coexisting phases. Here, we report lateral spin pumping by which angular momentum is transferred from FM domains into the AFM matrix during the phase transition of ultrathin FeRh films. In addition, FeRh is verified to be both an efficient spin generator and an efficient spin sink, by electrically probing vertical spin pumping from FM-FeRh into Pt and from Py into FeRh, respectively. A dramatic enhancement of damping related to AFM-FeRh is observed during the phase transition, which we prove to be dominated by lateral spin pumping across the FM/AFM interface. The discovery of lateral spin pumping provides insight into the spin dynamics of magnetic thin films with mixed-phases, and the significantly modulated damping advances its potential applications, such as ultrafast spintronics.

Record thermopower found in an IrMn-based spintronic stack

“…This effect has also been reported in other antiferromagnets and is attributed to volume-based anisotropy energies 27 . The highly localized magnetic behavior of antiferromagnets near their critical temperature [28][29][30][31][32] gives rise to exciting physical phenomena. Spin colossal magnetoresistance has been reported near the critical temperature in antiferromagnetic Cr 2 O 3 33 .…”

Electric-field control of spin dynamics during magnetic phase transitions

“…Besides the contribution from the extrinsic damping mechanisms, the intrinsic Gilbert damping also decreases slightly with the temperature as a result of the decreasing saturation magnetization. The overall change in the effective damping parameter comprises all three contributions, i.e., ∆α eff = ∆α int + ∆α lsp + ∆α tms , and the lateral spin pumping was found to be the dominant mechanism for damping modulation during the phase transition in FeRh ( 16 ).…”

“…Specifically, upon cooling, the nucleation and growth of antiferromagnetic domains take place in a fully ferromagnetic state. The resulting coexistence of the ferromagnetic and antiferromagnetic domains enhances two-magnon scattering due to the enhanced magnetic inhomogeneity ( 51 ) and enables the lateral spin pumping into the antiferromagnetic domains ( 16 ). Upon heating, the transition happens in a reversed manner.…”

“…In such damping process, the angular momentum is transferred from the ferromagnet into the spin sink at ferromagnetic resonance (FMR) ( 2 , 15 ). It has been shown recently that spin pumping can occur laterally in FeRh ( 16 ), a metallic alloy that has ferromagnetic and antiferromagnetic phases coexisting during the metamagnetic phase transition, where the spin current is transported from its ferromagnetic domain into the surrounding antiferromagnetic spin sink (as shown schematically in Fig. 1A ).…”

Local manipulation of metamagnetism by strain nanopatterning

“…28,29 This AFM-FM transition has been widely studied as well from a fundamental point of view. [30][31][32][33] The temperature at which the AFM order disappears (metamagnetic transition temperature, T*) can be tailored by the application of external magnetic fields, 34 changing composition/ doping, 35,36 electrochemical processes, 37 hydrostatic pressure 38 or biaxial strain imposed by the substrate. [39][40][41][42][43][44][45][46] The two latter effects are related to the change of the FeRh unit cell across the transition, being the unit cell parameter smaller in the low temperature AFM phase than in the high temperature FM phase.…”