Spinel antiferromagnets have long been at the center of research into strong spin-lattice coupling and orbital effects. Among other properties, these materials frequently demonstrate concomitant magnetic and structural phase transitions, heightened magneto-elastic or dielectric response functions, and low-temperature multiferroism. There is very little agreement on the microscopic picture to be associated with these effects, but recent work has shown that mesoscale inhomogeneity can play a key role in raising the susceptibilities of complex materials to external perturbations.
In this talk, I will be discussing recent work at the University of Illinois which establishes the importance of mesoscale heterogeneity in determining bulk magnetic properties of spinel ferrimagnets Mn3O4 and MnV2O4. This will first include a review of Raman and x-ray scattering results which reveal the existence of low-temperature magnetostructural transitions and magnetic force microscopy data which show the existence of stripe-like magnetic domains, before turning to our more recent neutron scattering and muon spin rotation (muSR) measurements. Our muSR work associates the emergence of stripe-like domains in Mn3O4 with a real space separation into magnetically ordered and disordered volumes, and further shows that the ordering fraction can be grown with the application of moderate-sized fields. With small angle neutron scattering, we observe Bragg signatures of domain wall order in the bulk of both materials, with wall separations on the ~100nm scale. Lastly, I will present data that demonstrates how domain wall motion can be used to drive these systems out of their low-temperature ferrimagnetic states, with an Hc which is highly sensitive to the applied field direction. I will correlate these results from microscopic probes to our recent investigation into non-equilibrium effects in the bulk magnetization, and discuss in the context of “colossal” control of magnetic properties of real materials.
Acknowledgments:
Research was supported by the National Science Foundation under Grant NSF DMR 1455264.
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2019-10-03T14:00:002019-10-03T15:00:00Identification and control of domain wall patterning in spinel ferrimagnets Event Information:
Spinel antiferromagnets have long been at the center of research into strong spin-lattice coupling and orbital effects. Among other properties, these materials frequently demonstrate concomitant magnetic and structural phase transitions, heightened magneto-elastic or dielectric response functions, and low-temperature multiferroism. There is very little agreement on the microscopic picture to be associated with these effects, but recent work has shown that mesoscale inhomogeneity can play a key role in raising the susceptibilities of complex materials to external perturbations.
In this talk, I will be discussing recent work at the University of Illinois which establishes the importance of mesoscale heterogeneity in determining bulk magnetic properties of spinel ferrimagnets Mn3O4 and MnV2O4. This will first include a review of Raman and x-ray scattering results which reveal the existence of low-temperature magnetostructural transitions and magnetic force microscopy data which show the existence of stripe-like magnetic domains, before turning to our more recent neutron scattering and muon spin rotation (muSR) measurements. Our muSR work associates the emergence of stripe-like domains in Mn3O4 with a real space separation into magnetically ordered and disordered volumes, and further shows that the ordering fraction can be grown with the application of moderate-sized fields. With small angle neutron scattering, we observe Bragg signatures of domain wall order in the bulk of both materials, with wall separations on the ~100nm scale. Lastly, I will present data that demonstrates how domain wall motion can be used to drive these systems out of their low-temperature ferrimagnetic states, with an Hc which is highly sensitive to the applied field direction. I will correlate these results from microscopic probes to our recent investigation into non-equilibrium effects in the bulk magnetization, and discuss in the context of “colossal” control of magnetic properties of real materials.
Acknowledgments:
Research was supported by the National Science Foundation under Grant NSF DMR 1455264.Event Location:
TRIUMF Auditorium