Temperature dependence of the inverse spin Hall effect in Ni80Fe20/Pt bilayers

J. E. GÓMEZ; L. AVILÉS-FÉLIX; A. BUTERA

New Orleans

Conferencia; 61st Annual Conference on Magnetism and Magnetic Materials; 2016

AIP

Temperaturedependence of the inverse spin Hall effect in Ni80Fe20/Pt bilayers  Javier E. Gómez1, Luis Avilés-Félix1 and AlejandroButera1,  1Centro AtómicoBariloche and Instituto Balseiro, Av. Bustillo9.500, 8400 Bariloche, Río Negro, Argentina                 We present a study of theevolution of the inverse spin Hall effect (ISHE) in platinum as a function oftemperature in a set of bilayer thin films made up of permalloy (Py) covered byPt. The samples were made using sputtering techniques on naturally oxidized Siwafers. Samples have a fixed Py thickness(tPy = 8 nm) and a varyingPt thickness (tPt= 1, 2,3, 4 and 5 nm). The ISHE voltage was induced by the spin pumping effectoccurring at the Py/Pt interface when the ferromagnetic layer is driven to itsferromagnetic resonance condition.               At room temperature, a positive ISHEvoltage is observed in all samples. When the temperature is decreased, thevalue of the signal also decreases, reaching a vanishing value at a temperatureT0 that depends strongly on the Pt thickness. We have found amaximum value of T0 = 215 K for tPt= 2 nm and a minimum T0 = 120 K fortPt= 5 nm. When thetemperature is further reduced the signal changes sign and reaches a minimum negativevalue at a characteristic temperature TM = 80 K, which isapproximately the same for all bilayers. However, the minimum value of the ISHEsignal that occurs at TM depends on the Pt thickness, tending to decrease when tPt is increased. Attemperatures below TM the signal increases sharply to positivevalues and remains positive down to T = 4K for all samples. Thetemperature where this sharp change occurs is the same for all films. TypicalISHE spectra measured at representative temperatures and a detailed temperatureevolution of the ISHE are shown in Fig 1 (a) and (b) respectively for thesample Ni80Fe20(8 nm)/Pt(3 nm).               Additional measurements suggestthat the Py layer contributes to the temperature evolution of the detected ISHEsignal. We discuss a possible explanation of the observed behavior based on theself induced signal on the Py layer, probably due to stress effects caused bythe different thermal expansion between the Si substrate and the metalliclayers.     Figure 1: (a)ISHE signal spectra of sample Ni80Fe20(8 nm)/Pt(3 nm)measured at different temperatures. (b) Detailed evolution of the maximum ISHEsignal as a function of the temperature.  Keywords: SPINPUMPING, FERROMAGNETIC RESONANCE, INVERSE SPIN HALL EFFECT