We report on the temperature dependence of the recently discovered spin Hall magnetoresistance in a yttrium iron garnet (YIG)/platinum (Pt) thin film. The YIG/Pt layers are an ideal choice as the combination of an insulating magnetic material and the high spin-orbit interaction in Pt gives a relatively large magnetoresistance and no electrical conduction occurs in the YIG. The temperature dependence of the magnetoresistance was measured between 1.4 K and 280 K from which the temperature dependence of the spin diffusion length in Pt has been extracted. We found that the best agreement between our data and the recently published [Chen et al., Phys. Rev. B 87, 144411 (2013)] theory of the spin Hall magnetoresistance is given by an assumed Elliot-Yafet mechanism of spin relaxation with temperature-independent spin Hall angle and spin mixing conductance. The best estimate for the spin diffusion length returns values between 0.57 and 3.85 nm.

Yttrium iron garnet has a very high Verdet constant, is transparent in the infrared and is an insulating ferrimagnet leading to its use in optical and magneto-optical applications. Its high Q-factor has been exploited to make resonators and filters in microwave devices, but it also has the lowest magnetic damping of any known material. In this article we describe the structural and magnetic properties of single crystal thin-film YIG where the temperature dependence of the magnetisation reveals a decrease in the low temperature region. In order to understand this complex material we bring a large number of structural and magnetic techniques to bear on the same samples. Through a comprehensive analysis we show that at the substrate -YIG interface, an interdiffusion zone of only 4–6 nm exists. Due to the interdiffusion of Y from the YIG and Gd from the substrate, an addition magnetic layer is formed at the interface whose properties are crucially important in samples with a thickness of YIG less than 200 nm.

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The response of Y 3 Fe 5 O 12 /Cu/Ni 81 Fe 19 trilayer structures to excitation by a femtosecond laser pulse has been studied in optical pump-probe experiments and compared with the response of Y 3 Fe 5 O 12 (YIG) and Ni 81 Fe 19 reference samples. The optical pump induces a partial demagnetization of the Ni 81 Fe 19 , a large thermal gradient within the YIG, and temperature differences across the interfaces within the sample stack. When a moderate magnetic field is applied close to normal to the sample plane, so as to quasialign the YIG magnetization with the field and cant the Ni 81 Fe 19 magnetization from the plane, ultrafast demagnetization initiates precession of the Ni 81 Fe 19 magnetization. The transient temperature profile within the samples has been modeled using a one-dimensional finite-element computational model of heat conduction, while the magnetization dynamics are well described by a macrospin solution of the Landau-Lifshitz-Gilbert equation. The precessional response of the Ni 81 Fe 19 layers within the trilayers and the Ni 81 Fe 19 reference sample are very similar for pump fluences of up to 1.5 mJ/cm 2 , beyond which irreversible changes to the magnetic properties of the films are observed. These results suggest that the spin Seebeck effect is ineffective in modifying the precessional dynamics of the present YIG/Cu/Ni 81 Fe 19 samples when subject to ultrafast optical excitation.