Kai Wang,Liqin Yan,Youguo Shi,Baogen Shen,Lunhua He,Fangwei Wang,Jun Lu,Tongyun Zhao,Zunming Lu
Among the 5d transition metal iridates, Sr2IrO4, which has a layered chalcogenide structure, has received much attention due to its strong spin–orbit coupling (SOC), which produces Mott insulating states and anomalous physical behaviors. In this paper, the microscopic magnetism of Sr2IrO4is studied with electron spin resonance (ESR) measurements. The Lande factorgof the ferromagnetic resonance signal of Sr2IrO4shows anomalous behavior compared to typical ferromagnets. It gradually decreases, and the corresponding resonance fieldHrincreases, with decreasing temperature. The various physical parameters. including the saturated magnetic fieldHsderived fromM-H,Hr, ΔHpp, thegfactor and the intensityIextracted from ESR spectra, are analyzed in detail. Eventually, it is revealed that the anomalous behavior of theg-factor is induced by in-plane Dzyaloshinsky–Moriya interaction (DMI) rather than the SOC effect.
Du Yu,Xie Fakang,Lu Mengfei,Lv Rongxian,Liu Wangxi,Yan Yuandong,Yan Shicheng,Zou Zhigang
Compressive strain, downshifting the d -band center of transition metal oxides, is an effective way to accelerate the sluggish kinetics of oxygen evolution reaction (OER) for water electrolysis. Here, we find that anisotropic thermal expansion can produce compressive strains of the IrO 6 octahedron in Sr 2 IrO 4 catalyst, thus downshifting its d- band center. Different from the previous strategies to create constant strains in the crystals, the thermal-triggered compressive strains can be real-timely tuned by varying temperature. As a result of the thermal strain accelerating OER kinetics, the Sr 2 IrO 4 exhibits the nonlinear ln j o - T −1 ( j o , exchange current density; T , absolute temperature) Arrhenius relationship, resulting from the thermally induced low-barrier electron transfer in the presence of thermal compressive strains. Our results verify that the thermal field can be utilized to manipulate the electronic states of Sr 2 IrO 4 via thermal compressive strains downshifting the d -band center, significantly accelerating the OER kinetics, beyond the traditional thermal diffusion effects.
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