Enhanced magnon spin transport in NiFe2O4 thin films on a lattice-matched substrate

Abstract

We investigate magnon spin transport in epitaxial nickel ferrite (NiFe 2 O 4 , NFO) films grown on magnesium gallate spinel (MgGa 2 O 4 , MGO) substrates, which have a lattice mismatch with NFO as small as 0.78%, resulting in the reduction of antiphase boundary defects and thus in improved magnetic properties in the NFO films. In the nonlocal transport experiments, enhanced signals are observed for both electrically and thermally excited magnons, and the magnon relaxation length (λ m ) of NFO is found to be around 2.5 µm at room temperature. Moreover, at both room and low temperatures, we present distinct features from the nonlocal spin Seebeck signals which arise from magnonpolaron formation. Our results demonstrate excellent magnon transport properties (magnon spin conductivity, λ m and spin mixing conductance at the interface between Pt) of NFO films grown on a lattice-matched substrate that are comparable with those of yttrium iron garnet.

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

“…The value of ξ deduced from the fits is in the range of 400 to 700 nm. This is lower than the recently reported value obtained from nonlocal magnon spin transport measurements in sputter deposited NFO films (∼3 µm) [26,50]. Such discrepancy between local LSSE and nonlocal magnon spin transport results has also been observed for YIG [28,47] and can be explained by the different nature of the experiments.…”

All‐Electrical Magnon Transport Experiments in Magnetically Ordered Insulators

“…One example in this regard are nickel ferrite (NFO) thin films, where magnesium gallate substrates significantly reduce the Gilbert damping and thus increase the magnon spin lifetime. [236] In all-electrical magnon transport experiments, [224] NFO grown on such latticematched substrates exhibits similar properties than YIG thin films. Similar enhancement in magnon-transport properties may be found in other materials, as further development in the growth of AFIs on lattice-matched substrates has the potential to significantly enhance magnon transport properties in thin films and match their bulk counterparts.…”

“…After the first theoretical prediction and experimental demonstration of all-electrical magnon transport in NM/MOI heterostructures, [61][62][63] experiments in this regard were conducted not only in ferri-MOIs [23,[64][65][66][67][68][69][70][72][73][74][75][76]181,223,224] but also in AFIs. [71,[77][78][79][80]171] In this way, we obtained access to studying magnon transport, corresponding to GHz or even THz frequencies, utilizing magnetotransport techniques and DC charge currents.…”

Magnon polarons in the spin Peltier effect

“…Magnetoelastic coupling (MEC), the interaction between spin waves (magnons) and lattice waves (phonons), was first investigated more than half a century ago [1][2][3] and has renewed attention in spintronics . By the MEC, magnons and phonons, in the vicinity of the crossings of their dispersion relations, are hybridized into quasiparticles called magnon polarons that share mixed magnonic and phononic characters [6,8,[10][11][12][20][21][22][23][24][25][26][27][28][29][30]. Magnon polarons can convey spin information with velocities close to those of phonons, much faster than the magnon velocities in the dipolar magnon regime [7,8,14,15].…”