Coupled phonons and magnetic orderings in GaFeO3: Raman and magnetization studies

Abstract

Magnetoelectric (ME) materials with ferroelectric and magnetic transition temperatures near room temperature are of current interest in research due to their technological importance and potential applications. Herein, we report the coupled magnetic ordering and phonons in gallium ferrite (GaFeO3), a near room temperature ME perovskite, using magnetization and inelastic light scattering measurements as a function of temperature. Temperature-dependent magnetization behavior studied in a wide temperature range of 5–395 K at both field-cooled (FC) and zero-field-cooled (ZFC) conditions using different static magnetic fields confirms the magnetic transition temperature Tc at 220 K. On temperature dependent Raman spectroscopy, no significant changes in Raman spectra were observed at an elevated temperature that can be attributed to the absence of structural phase transition. Instead of expected anharmonic behavior, several librational (rigid rotation) and stretching modes of rigid BO6 units were found to be hardening below Tc, suggesting the significant magnetoelastic coupling contributions to phonon frequencies. The asymmetric stretching mode at 753 cm−1 is found to have larger spin-phonon coupling contribution (λ∼2.93), while the lattice mode at 153 cm−1 and external librational mode at 240 cm−1 had the lowest effect (λ∼0.88).

Strong spin–phonon coupling in Gd-filled nanotubes

“…38 In particular, the changes in a phonon mode fre quency of a magnetic compound as a function of temperature can be attributed due to intrinsic anharmonicity (ω anh ) and spin phonon coupling (ω s ph ) because of magnetic spin ordering at criti cal temperature. This behavior has already been reported in various magnetic compounds such as GaFeO 3 , 19 SrRuO 3 , 39 BaFe 12 O 19 , 40 Al 0.5 Ga 0.5 FeO 3 , 41 etc.…”

“…Gext , yet significant when compared to multiferroic compounds reported earlier. 19,39,40 It is interesting to note that the spin phonon coupling values are approximately three times higher than Kondo lattice. This will be discussed in detail in a future publication.…”

“…18 Particularly for a magnetic material, the phonon mode frequency variation concerning temperature occurs due to anharmonicity (Δω anh ) originating from effective lattice interaction in the disordered structure and a spin phonon coupling contribution (Δω s ph ) coming from the spin ordering of the mag netic ions. 19 Thus, by performing low temperature Raman spectro scopy on the magnetic molecules filled DWNTs, we can analyze the individual contributions and can therefore determine the spin phonon coupling constant through Heisenberg's exchange spin spin correlation function 〈S i .S j 〉 in conjugation with magneti zation studies.…”

Tuning the magnetic phase transition above room temperature through Fe and Mn modification in gallium ferrite with reduced leakage current

“…Prior to performing, Rietveld refinement, the XRD pattern was analyzed with the JCPDF package. The peaks were found to match well with the JCPDF #761005, suggesting the orthorhombic phase formation belonging the group Pc2 1 n. Rietveld refined graph of GFO1 is taken from our earlier report [23]. In the samples, no secondary peaks in the diffraction pattern were found until x ≤ 1.2 showing single phase GFO.…”

Spin glass behavior and exchange bias effect in GaFeO3‐type iron oxide

“…Hence, the magnetic properties of GF x O are closely related to the occupation of the cationic sites. Therefore, cation site disorder dictates the magnetic property, which has been studied extensively by various researchers using GF x O powders, 20–23 single crystals, 24,25 and thin films 26–28 …”