Magnetodielectric effect and phonon properties of compressively strained EuTiO3thin films deposited on (001)(LaAlO3)0.29

Abstract

Compressively strained epitaxial (001) EuTiO3 thin films of tetragonal symmetry have been deposited on (001) (LaAlO3)0.29-(SrAl 1/2 Ta 1/2 O3)0.71 (LSAT) substrates by reactive molecular-beam epitaxy. Enhancement of the Néel temperature by 1 K with 0.9% compressive strain was revealed. The polar phonons of the films have been investigated as a function of temperature and magnetic field by means of infrared reflectance spectroscopy. All three in-plane polarized infrared active phonons show strongly stiffened frequencies compared to bulk EuTiO3 in accordance with first principles calculations. The phonon frequencies exhibit gradual softening on cooling leading to an increase in static permittivity. A new polar phonon with frequency near the TO1 soft mode was detected below 150 K. The new mode coupled with the TO1 mode was assigned as the optical phonon from the Brillouin zone edge, which is activated in infrared spectra due to an antiferrodistortive phase transition and due to simultaneous presence of polar and/or magnetic nanoclusters. In the antiferromagnetic phase we have observed a remarkable softening of the lowest-frequency polar phonon under an applied magnetic field, which qualitatively agrees with first principles calculations. This demonstrates the strong spin-phonon coupling in EuTiO3, which is responsible for the pronounced dependence of its static permittivity on magnetic field in the antiferromagnetic phase.

Spin-phonon coupling in epitaxialSr0.6Ba0.4MnO3thin films

“…Newly activated phonons appear near 220 and 340 cm −1 below 100 and 150 K, respectively. constant arising from the increase of the TO1 mode frequency below T N is also observed in archetypal spin-phonon coupling oxide EuTiO 3 [26,27].…”

High frequency magneto-dielectric effects in self-assembled ferrite-ferroelectric core-shell nanoparticles

“…A sample of dimensions 10.7 mm × 4.3 mm and a thickness of 0.43 mm was used. Data on ε r vs f for a series of H over the range [16][17][18][19][20][21][22][23][24] GHz are shown in Fig. 3.…”

“…Measurements of the real (ε r ) and imaginary (ε r ) parts of the relative permittivity have been carried out over [16][17][18][19][20][21][22][23][24] GHz with rectangular platelets of samples of as-assembled powder in waveguides and from data on transmission and reflection coefficients of microwave power through the waveguide. The…”

“…There have been several reports in recent years on the observation of MDE due to phase transitions in single phase multiferroics [16][17][18][19] or magnon-phonon coupling in antiferromagnets. 21,22 But there have been very few reports on the observation and modeling of MDE in composite multiferroics. In a composite with ferromagnetic La-Sr-manganite and a ferroelectric, the strain mediated ME coupling was reported to show 9.5% change in the permittivity under H = 9 T. 23 Modeling efforts on MDE in composites so far include thermodynamic formalisms based on the Landau-Devonshire theory applied to cobalt particles dispersed in barium titanate (BTO) matrix 24 and a non-linear thermodynamic approach to estimate the magneto-capacitance effect in BTO or PZT films on substrates of ferromagnetic alloys.…”

“…[16][17][18][19][20][21][22][23][24][25] It is a powerful tool for investigations on the nature of direct-ME effects in single phase and composite multiferroics. There have been several reports in recent years on the observation of MDE due to phase transitions in single phase multiferroics [16][17][18][19] or magnon-phonon coupling in antiferromagnets.…”