Matthias Opel (SIMES Seminar)

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Date/Time
Date(s) - Jun 28 2017
1:30 PM - 2:30 PM

Location
Whitney Room, room 310, Building 40, SLAC National Accelerator Lab

Category(ies)


Spin-Hall Magnetoresistance (SMR) in Magnetic Insulators

Matthias Opel

Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching, Germany
Email: matthias.opel@wmi.badw.de, web site: http://www.wmi.badw.de/research/spintronics.htm

The interplay between charge and spin currents at the interface between paramagnetic metals and magnetic insulators results in novel spintronic effects, such as the recently discovered spin-Hall magnetoresistance (SMR). It manifests itself in an unexpected dependence of the resistivity of a paramagnetic Pt layer (representing the most widely used spin-Hall material) on the magnetization of an adjacent ferromagnet, such as Y3Fe5O12 or NiFe2O4 [1,2]. Its interpretation relies on the reflection or absorption of spin currents at the interface [1-3].

We first discuss our latest results on the proximity magnetism and the SMR effect in the Pt/Y3Fe5O12 system from a comprehensive investigation of different samples as a function of the thickness of the Pt layer and the stacking order of the Pt and Y3Fe5O12 layers. We study the X-ray absorption spectra (XAS) and the X-ray magnetic circular dichroism (XMCD) at the Pt L2,3 edges [4] and perform measurements of the angle-dependent magnetoresistance (ADMR) [1,2,5]. The results are fully consistent with the prediction of the SMR theory [4] and demonstrate that the SMR effect is governed by the net magnetization in the collinear ferrimagnet Y3Fe5O12.

Second, in the canted ferrimagnet Gd3Fe5O12 the ADMR signal shifts by 90° at the magnetic compensation temperature [6]. Using atomistic spin simulations and XAS/XMCD experiments, we understand this observation in terms of the magnetic field and temperature dependent orientation of magnetic moments on different magnetic sublattices [6]. This enables an SMR-based investigation of non-collinear magnetic textures.

Third, in the antiferromagnetic insulators NiO and Fe2O3 we always observe this 90° shift of the ADMR signal at high magnetic fields. Since in the spin-flop phase the sublattice magnetizations are oriented perpendicular to the external magnetic field, this evidences that the SMR effect is governed by the sublattice magnetizations.

This work is supported by the European Synchrotron Radiation Facility (ESRF) via HE-3784, HC‑1500, and HC-2058, as well as the Deutsche Forschungsgemeinschaft (DFG) via SPP 1538.

 

References:

[1]   H. Nakayama et al., Phys. Rev. Lett. 110, 206601 (2013)

[2]   M. Althammer et al., Phys. Rev. B 87, 224401 (2013).

[3]   Y.-T. Chen et al., Phys. Rev. B 87, 144411 (2013).

[4]   S. Geprägs et al., Appl. Phys. Lett. 101, 262407 (2012) and arXiv:1307.4869 (2013).

[5]   S. Meyer et al., Appl. Phys. Lett. 104, 242411 (2014).

[6]   K. Ganzhorn et al., Phys. Rev. B 94, 094401 (2016).