The authors report on a systematic investigation of the longitudinal spin Seebeck effect (LSSE) in a GGG(Gd3Ga5O12)/GdIG(Gd3Fe5O12)/Pt film series exhibiting an in‐plane magnetic easy axis with a compensation temperature (TComp) that decreases from 270 to 220 K when decreasing GdIG film thickness from 272 to 31 nm, respectively. For all the films, the LSSE signal flips its sign below TComp. The authors demonstrate a universal scaling behavior of the temperature dependence of LSSE signal for the GdIG films around their respective TComp. Additionally, the authors demonstrate LSSE in a 31 nm GdIG film grown on a lattice‐mismatched GSGG (Gd3Sc2Ga3O12) substrate that exhibits an out‐of‐plane magnetic easy axis at room temperature. However, this sample reveals a spin reorientation transition where the magnetic easy axis changes its orientation to in‐plane at low temperatures. A clear distinction is observed in the LSSE signal for the GSGG/GdIG(31 nm)/Pt heterostructure, relative to GGG/GdIG(31 nm)/Pt showing an in‐plane magnetic easy axis. The findings underscore a strong correlation between the LSSE signal and the orientation of magnetic easy axis in compensated ferrimagnets and opens the possibility to tune LSSE through effective anisotropy.
Understanding impacts of phase transition, phase coexistence, and surface magnetism on the longitudinal spin Seebeck effect (LSSE) in a magnetic system is essential to manipulate the spin to charge current conversion efficiency for spincaloritronic applications. We aim to elucidate these effects by performing a comprehensive study of the temperature dependence of LSSE in biphase iron oxide (BPIO = -Fe2O3 + Fe3O4) thin films grown on Si (100) and Al2O3 (111) substrates. A combination of temperature-dependent anomalous Nernst effect (ANE) and electrical resistivity measurements show that the contribution of ANE from the BPIO layer is negligible compared to the intrinsic LSSE in the Si/BPIO/Pt heterostructure even at room temperature. Below the Verwey transition of the Fe3O4 phase, the total signal across BPIO/Pt is dominated by the LSSE. Noticeable changes in the intrinsic LSSE signal for both Si/BPIO/Pt and Al2O3/BPIO/Pt heterostructures around the Verwey transition of the Fe3O4 phase and the antiferromagnetic (AFM) Morin transition
We report broadband magnetic resonance
in polycrystalline Sr
2
FeMoO
6
measured over the
wide temperature (
T
= 10–370 K) and frequency
(
f
=
2–18 GHz) ranges. Sr
2
FeMoO
6
was synthesized
by the sol–gel method and found to be ferromagnetic below
T
C
= 325 K. A coplanar waveguide-based broadband
spectrometer was used to record the broadband electron spin resonance
(ESR) both in frequency sweep and field sweep modes. From the frequency
sweep mode at fixed dc magnetic fields, we obtain the spectroscopic
splitting factor
g
∼ 2.02 for
T
≥
T
C
K, which confirms the 3+
ionic state of Fe in the material. The effective
g
value was found to decrease monotonically with decreasing temperature
in the ferromagnetic regime. Resonance frequency decreases and the
line width of the spectra increases as the temperature decreases below
T
C
. At room temperature (RT) and above, the line
width (Δ
H
) of the ESR signal increases linearly
with frequency, giving Gilbert damping constant α ∼0.032
± 0.005 at RT. However, at lower temperatures, a minimum emerges
in the Δ
H
vs frequency curve, and the minimum
shifts to a higher frequency with decreasing temperature, confining
the linear frequency regime to a narrow-frequency regime. Additional
inhomogeneous broadening and low-field-loss terms are needed to describe
the line width in the entire frequency range.
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