Enhancement in Thermally Generated Spin Voltage at Pd/NiFe${}_2$O${}_4$ Interfaces by the Growth on Lattice-Matched Substrates

Abstract

Efficient spin injection from epitaxial ferrimagnetic NiFe${}_2$O${}_4$ thin films into a Pd layer is demonstrated via spin Seebeck effect measurements in the longitudinal geometry. The NiFe${}_2$O${}_4$ films (60 nm to 1 $\mu$m) are grown by pulsed laser deposition on isostructural spinel MgAl${}_2$O${}_4$, MgGa${}_2$O${}_4$, and CoGa${}_2$O${}_4$ substrates with lattice mismatch varying between 3.2% and 0.2%. For the thinner films ($\le$ 330 nm), an increase in the spin Seebeck voltage is observed with decreasing lattice mismatch, which correlates well with a decrease in the Gilbert damping parameter as determined from ferromagnetic resonance measurements. High resolution transmission electron microscopy studies indicate substantial decrease of antiphase boundary and interface defects that cause strain-relaxation, i.e., misfit dislocations, in the films with decreasing lattice mismatch. This highlights the importance of reducing structural defects in spinel ferrites for efficient spin injection. It is further shown that angle-dependent spin Seebeck effect measurements provide a qualitative method to probe for in-plane magnetic anisotropies present in the films.

arXiv comment18 pages, 6 figures

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Cited by in corpus (3)

• Spin Seebeck effect and magnon diffusion length in ${\mathbf{Fe}}_3{\mathbf{O}}_4$
• Measurement of the heat flux normalised spin Seebeck coefficient of thin films as a function of temperature
• Magnetism and nonlinear charge transport in NiFe2O4/γ-Al2O3/SrTiO3 heterostructure: Toward Spintronic Applications