Detection of induced paramagnetic moments in Pt onY3Fe5O12via x-ray magnetic circular dichroism

Abstract

Magnetic moments in an ultra-thin Pt film on a ferrimagnetic insulator Y3Fe5O12 (YIG) have been investigated at high magnetic fields and low temperatures by means of X-ray magnetic circular dichroism (XMCD). We observed an XMCD signal due to the magnetic moments in a Pt film at the Pt L3-and L2-edges. By means of the element-specific magnetometry, we found that the XMCD signal at the Pt L3-edge gradually increases with increasing the magnetic field even when the field is much greater than the saturation field of YIG. Importantly, the observed XMCD intensity was found to be much greater than the intensity expected from the Pauli paramagnetism of Pt when the Pt film is attached to YIG. These results imply the emergence of induced paramagnetic moments in Pt on YIG and explain the characteristics of the unconventional Hall effect in Pt/YIG systems.

Interfacial ferromagnetism and atomic structures in high-temperature grown Fe3O4/Pt/Fe3O4 epitaxial trilayers

“…This is because, if the proximity-induced Pt ferromagnetism exists in these systems, the ISHE voltage induced by the spin-current phenomena may be contaminated by the anisotropic magnetoresistance or anomalous Nernst effect due to the magnetized Pt [3,4,8,21,[21][22][23][24][25][26][27][28]. Hence, the separation of the spincurrent contribution from magnetic-proximity-effect contribution is important in spintronics, and the detection of Pt ferromagnetism in the Pt/magnetic-oxide systems has attracted much attention [29][30][31][32][33][34][35][36][37][38]. Recent studies demonstrated that, in Pt/Y 3 Fe 5 O 12 , Pt/NiFe 2 O 4 , Pt/CoFe 2 O 4 , and Pt/Fe 3 O 4 , the proximity-induced parasitic contribution is negligibly small in comparison with the spin-current contribution to SMR or SSE [4, 8, 15, 17, 24-27, 29, 31-35, 39].…”

“…Since the end of 1990s, a number of XMCD and XRMR studies focusing on Pt/3d-ferromagnetic-metal (Fe, Ni, Co, and Ni 81 Fe 19 ) junction systems have been reported and the Pt ferromagnetism in these systems has been established [44][45][46][47][48][49][50][51][52][53][54][55][56]. Recently, these techniques were applied for the Pt/magnetic-oxide systems: Pt/Y 3 Fe 5 O 12 [29][30][31]36], Pt/NiFe 2 O 4 [32,33,37], Pt/CoFe 2 O 4 [34,35,37], Pt/MnFe 2 O 4 [37], and Pt/Fe 3 O 4 [37]; in contrast to the Pt/3d-ferromagnetic-metal systems, the proximity-induced Pt ferromagnetism in these Pt/magnetic-oxide systems was found to be undetectably small when the effect of Pt oxidization is negligible [30,31]. These results suggest that small magnetization of the magnetic oxides is disadvantageous to inducing proximity ferromagnetism in the adjacent Pt layer; Y 3 Fe 5 O 12 , NiFe 2 O 4 , CoFe 2 O 4 , and Fe 3 O 4 are insulators or highly-resistive conductors [57][58][59] and their volume magnetization is much smaller than that of the 3d-ferromagnetic-metals [60].…”

Hard X-ray Photoelectron Spectroscopy Study of Pt/Y3Fe5O12

“…Such behavior is not observed for a Pt film in contact with a nonmagnetic substrate, Gd 3 Gd 5 O 12 (GGG). Besides, the Pt/YIG system exhibits an unconventional Hall effect, whose magnetic-field dependence scales like a Brillouin function (not the magnetization curve of YIG) under high magnetic fields [9,10]. The feature is totally different from the normal Hall effect for Pt with a non-magnet (GGG) contact [10].…”

“…Note that this result supports the proposed origin of the anomalous Hall effect. That is, metallic Fe can act as a paramagnetic impurity in the Pt layer, giving rise to a skew scattering for itinerant electrons in Pt [10].…”

“…Besides, the Pt/YIG system exhibits an unconventional Hall effect, whose magnetic-field dependence scales like a Brillouin function (not the magnetization curve of YIG) under high magnetic fields [9,10]. The feature is totally different from the normal Hall effect for Pt with a non-magnet (GGG) contact [10]. A possible origin is the presence of Fe impurities from YIG, either in the Pt layer or at the Pt/YIG interface, that behaves as independent paramagnetic moments, causing the anomalous Hall effect due to skew scatterings [11].…”