Effects of magnetic field and twin domains on magnetostructural phase mixture inMn3O4: Raman scattering studies of untwinned crystals

Abstract

The ferrimagnetic spinel Mn3O4 exhibits large and anisotropic changes in electronic and structural properties in response to an applied magnetic field. These changes are thought to result from the field-dependent tuning-via strong spin-lattice coupling-between two nearly degenerate magnetostructural phases. Recent variable-magnetic-field studies of Mn3O4 have been performed on melt-grown crystals, which can exhibit twin domains due to a Jahn-Teller structural transition below the melting temperature. Because of the near degeneracy of the magnetostructural phases, however, strain associated with the twin domains likely affects the magnetic responses of Mn3O4. In this report, we present a variable-magnetic-field Raman scattering study of untwinned Mn3O4 crystals grown out of a flux below the Jahn-Teller structural transition. We measure distinct q = 0 magnetic and vibrational excitation spectra for each isolated magnetostructural phase of untwinned Mn3O4 crystals and determine the symmetries of the observed excitations. We determine how the magnetostructural phase mixture changes in response to magnetic fields applied in the magnetic easy plane. Lastly, by comparing results on flux-and melt-grown Mn3O4 crystals, we show that the intrinsic mixture of the two magnetostructural phases is indeed strongly influenced by the presence of twin domains.

Real-space magnetic imaging of the multiferroic spinels MnV2O4 and Mn3O4Wolin1, Wang2, Naibert3 et al. 2018Phys. Rev. MaterialsSelf Cite59250View full textAdd to dashboardCite

“…Similar to our observations in MnV 2O4, the tweed stripe pattern in Mn3O4 is eliminated by cooling in a sufficiently strong magnetic field (B=20kG). This is consistent with the observation of nearly degenerate orthorhombic phases in Mn 3O4, and the selection of a universal orthorhombic distortion axis with applied field [34,52]. The relationship between the tetragonal domains and the magnetic pattern is further evidence of the important role that mechanical strain plays in the low-temperature magnetic stripe formation and magnetic properties of these Mn-based spinels.…”

“…Figure 4 is a composite MFM image of the Mn 3O4 sample created by stitching together multiple individual MFM scans recorded in succession. The Mn3O4 sample was cooled in the presence of a weak magnetic field, B=2kG from above T=40K to T=18K; this is well into the cell-doubled orthorhombic ferrimagnetic phase, as determined by previous measurements [34,41,52]. We observe stripe modulations very similar to those observed in MnV 2O4.…”

“…cell-doubled orthorhombic phases at low temperatures [52], consistent with the presence of a mesoscale structural modulation in this material. In MnV 2O4, TEM measurements revealed the coexistence of tetragonal twinning domains with different c-axis orientations [42], and the sensitivity to strain we observe in our measurements of MnV 2O4 support the conclusion that the nanoscale magnetic modulation we observe in this material is associated with an underlying structural modulation.…”

Domain Wall Patterning and Giant Response Functions in Ferrimagnetic Spinels

“…These trends and the weak temperature hysteresis are largely in line with a collection of Raman spectroscopy, diffraction, and macrostrain measurements in the literature tracking the magnetostructural transitions in each material. [23,24,32,35,40] It is important to note that intensity variations in the annular profiles can be affected both by changes in the number of domain walls, which alters the overall intensity, as well as changes in the average domain size, which will alter the radial profile of the intensity distribution. Figure 3 displays the dependence of the scattering intensity on momentum Q in various directions for both materials.…”

Influence of laser‐induced heating on MnO nanoparticles

“…In the investigation of MnO, its related compounds, and different oxides of manganese such as MnO 2 , Mn 2 O 4 , and Mn 3 O 4 exist two basic trends. In the first one, laser power density has been kept as low as possible to avoid changes in samples, or in the second one, the influence of laser‐induced heating (with constant laser power and elongated time exposure) has been investigated on samples characteristics in MnO 2 , Mn 3 O 4 , and Mn 5 O 8 , whereas in the paper of Buciuman et al, three different laser lines are used.…”