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Updated: May 3, 2026
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Measuring Magnetically-Tuned Ferroelectric Polarization in Liquid Crystals
Published on: August 15, 2018
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Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo2 Laves phases
S L Driver1, J Herrero-Albillos, C M Bonilla
1Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK.
Summary
Magnetic phase transitions in rare earth cobalt (RCo2) Laves phases are linked to crystallographic changes, enabling multiferroic behavior. Studies on NdCo2 and ErCo2 reveal distinct transition types and mechanisms driving these coupled ferroelastic and magnetic properties.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Magnetism and Magnetic Materials
Background:
- RCo2 Laves phases exhibit magnetic phase transitions associated with crystallographic space group changes.
- These transitions can fulfill conditions for multiferroic behavior by combining ferro/antiferromagnetism, ferroelectricity, and ferroelasticity.
- Understanding the interplay between magnetic and structural properties is crucial for designing novel multiferroic materials.
Purpose of the Study:
- To analyze lattice parameter data and elastic/anelastic properties of NdCo2 and ErCo2 from a multiferroic perspective.
- To investigate the nature of magnetic and structural phase transitions in these RCo2 compounds.
- To elucidate the coupling mechanisms between magnetic and structural order parameters driving multiferroic behavior.
Main Methods:
- Analysis of existing lattice parameter data from literature.
- New measurements of elastic and anelastic properties using resonant ultrasound spectroscopy (RUS).
- Thermodynamic analysis of symmetry-breaking shear strains and elastic softening.
Main Results:
- The cubic to tetragonal transition in NdCo2 is near tricritical, while the cubic to rhombohedral transition in ErCo2 is first order.
- Elastic softening and acoustic loss are explained by intrinsic softening and ferroelastic twin-wall motion.
- Deviations in softening suggest cooperative Jahn-Teller distortions in NdCo2 and a tweed microstructure in ErCo2.
Conclusions:
- The multiferroic behavior in RCo2 Laves phases arises from the coupling of magnetic and structural order parameters.
- The observed transitions and associated phenomena are consistent with a single magnetic order parameter coupled to a structural order parameter.
- This coupling drives a single multiferroic phase transition, even in the presence of separate instabilities.
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