Magnetic resonance study of bulk and thin film EuTiO₃

Abstract

Magnetic resonance spectra of EuTiO3 in both bulk and thin film form were taken at temperatures from 3-350 K and microwave frequencies from 9.2-9.8 and 34 GHz. In the paramagnetic phase, magnetic resonance spectra are determined by magnetic dipole and exchange interactions between Eu 2+ spins. In the film, a large contribution arises from the demagnetization field. From detailed analysis of the linewidth and its temperature dependence, the parameters of spin-spin interactions were determined: the exchange frequency is 15-15.5 GHz and the estimated critical exponent of the spin correlation length is  0.5. In the bulk samples, the spectra exhibited a distinct minimum in the linewidth at the Néel temperature, TN  5.5 K, while the resonance field practically does not change even on cooling below TN. This is indicative of a small magnetic anisotropy  320 G in the antiferromagnetic phase. In the film, the magnetic resonance spectrum is split below TN into several components due to excitation of the magnetostatic modes, corresponding to a non-uniform precession of magnetization. Moreover, the film was observed to degrade over two years. This was manifested by an increase of defects and a change in the domain structure. The saturated magnetization in the film, estimated from the magnetic resonance spectrum, was about 900 emu/cm 3 or 5.5 B/unit cell at T = 3.5 K.

Light Emitting Rare Earth Doped K3GdF6:Eu3+ for Spectral Mapping/Imaging Studies

“…The broadness in the line width of the spectrum obtained for the X band can be attributed to the minimal energy difference between the Zeeman energy ( g β H ≈ 0.32 cm –1 ) in this band and the energy of the dipole interaction between Gd 3+ spins ( β 2 g 2 S 2 r 3 ≈ 0.42 cm –1 ), where β is the Bohr magneton, g is the g factor, and r is the distance between the ions. In addition to the above reason, the dipole type anisotropic spin–spin interaction between the paramagnetic ions may also be the reason for such broad spectral features …”

“…In addition to the above reason, the dipole type anisotropic spin−spin interaction between the paramagnetic ions may also be the reason for such broad spectral features. 58 By harnessing the cooperative interplay between optical and superparamagnetic phenomena, the dual-functional K 3 GdF 6 :5% Eu 3+ double perovskite offers flexible platforms for tailoring interactions between light and matter and magnetic responses at the nanoscale. Blending optical and superparamagnetic properties within a single entity shows the potential to tackle complex challenges and introduce new attributes.…”