Simultaneous observation of anti-damping and inverse spin Hall effect in La0.67Sr0.33MnO3/Pt bilayers

Abstract

Manganites have shown potential in spintronics due to their low damping and insulating characteristics. Here, we studied the damping properties of La0.67Sr0.33MnO3/Pt bilayer samples which are prepared using oxide molecular beam epitaxy. We have observed decrease in damping coefficient (α) with increase in Pt thickness. Further, we investigated inverse spin Hall effect (ISHE) and observed that ISHE signal gets enhanced with Pt thickness. We observed maximum spin pumping voltage of 20.05 µV for the sample with Pt thickness of 3 nm. We have evaluated spin Hall angle for these samples. Introduction: Pure spin current based devices are potential for faster and low power consumption [1]. Generation of pure spin current has been demonstrated by ferromagnetic resonance (FMR) through spin pumping mechanism [2]. This pure spin current can loss their spin angular momentum in the presence of high spin orbit coupling (SOC) material e.g. Pt, W, Ta. The loss of spin angular momentum can develop voltage by asymmetric scattering of spins, which is known as inverse spin Hall effect (ISHE) [3]. So far studies have been concentrated mostly on Pt and FM metals [4]. However, magnetic oxides are less explored. La0.67Sr0.33MnO3 (LSMO) is well known FM oxide for exhibiting high Curie temperature (TC=350 K) and nearly 100% spin polarization (in bulk) [5]. In this work, in order to get high spin Hall angle, high resistive Pt film is grown on LSMO thin film. Experimental details: LSMO (20 nm)/Pt (tPt = 0, 3 and 10 nm) bilayer samples have been prepared on SrTiO3(001) substrate using an oxygen plasma assisted molecular beam epitaxy system. ISHE measurements are performed using home modified coplanar wave-guide (CPW) based ferromagnetic resonance (FMR) spectroscopy [6]. Results: We have studied the static and dynamic properties of the LSMO/Pt systems. A decrease in α has been observed with increase in Pt thickness. We performed angle dependent ISHE at frequency of 7 GHz. From angle dependent ISHE measurement spin Hall angle were calculated 0.033 and 0.014 for samples with 3 and 10 nm of Pt, respectively.