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Nonreciprocal Directional Dichroism in Magnetoelectric Spin Glass
Y Sawada1, S Kimura1, K Watanabe1
1Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Physical Review Letters
|December 3, 2022
Summary
Magnetoelectric spin glass exhibits unique optical properties. The study shows nonreciprocal directional dichroism (NDD) arises from magnetoelectric toroidal order, not magnetic-dipole order.
Area of Science:
- Condensed matter physics
- Magnetoelectric materials
- Optical spectroscopy
Background:
- Nonreciprocal directional dichroism (NDD) is a phenomenon observed in certain magnetic materials.
- Previous studies linked NDD to long-range magnetic-dipole order or induced toroidal moments via external fields.
- The magnetoelectric spin glass Ni_{0.4}Mn_{0.6}TiO_{3} presents a unique system for studying NDD.
Purpose of the Study:
- To investigate the origin of NDD in the magnetoelectric spin glass Ni_{0.4}Mn_{0.6}TiO_{3}.
- To determine if NDD can exist without conventional long-range magnetic-dipole order.
- To explore the role of magnetoelectric field-cooling in inducing specific orders.
Main Methods:
- Optical absorption spectroscopy in visible and near-infrared light.
- Measurements performed on Ni_{0.4}Mn_{0.6}TiO_{3} under various field-cooled conditions.
- Analysis of NDD at zero external field post magnetoelectric field-cooling.
Main Results:
- The spin glass system Ni_{0.4}Mn_{0.6}TiO_{3} displayed NDD at zero field after magnetoelectric field-cooling.
- This NDD was observed in the absence of long-range magnetic-dipole order.
- The findings differentiate from NDD mechanisms requiring magnetic-dipole order or crossed fields.
Conclusions:
- The observed NDD in Ni_{0.4}Mn_{0.6}TiO_{3} originates from magnetoelectrically induced ferroic order of magnetic toroidal moments.
- Conventional magnetic-dipole order is not a prerequisite for observing NDD in this system.
- This study highlights a novel pathway for achieving NDD through magnetoelectric coupling.
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