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  • Successive Phase Transitions and Multiferroicity in Deformed Triangular-Lattice Antiferromagnets Ca 3 MNb 2 O 9 (M=Co, Ni) with Spatial Anisotropy
Title: Successive Phase Transitions and Multiferroicity in Deformed Triangular-Lattice Antiferromagnets Ca 3 MNb 2 O 9 (M=Co, Ni) with Spatial Anisotropy
We constructed the magnetic field-temperature phase diagrams of new quasi-two-dimensional isosceles triangular lattice antiferromagnets (TLAF) Ca 3 MNb 2 O 9 (M=Co, Ni) from dc and ac magnetic susceptibilities, specific heat, dielectric constant, and electric polarization measurements on single crystalline samples. Ca 3 CoNb 2 O 9 with effective spin-1/2 Co 2+ ions undergoes a two-step antiferromagnetic phase transition at T N1 = 1.3 K and T N2 = 1.5 K and enters a stripe ordered state at zero magnetic field. With increasing field, successive magnetic phase transitions, reminiscent of the up-up-down ( uud ) and the oblique phases, are observed. The dielectric constant of Ca 3 CoNb 2 O 9 shows anomalies related to the magnetic phase transitions, but clear evidence of ferroelectricity is absent. Meanwhile, Ca 3 NiNb 2 O 9 with spin-1 Ni 2+ ions also shows a two-step antiferromagnetic transition at T N1 = 3.8 K and T N2 = 4.2 K at zero field. For Ca 3 NiNb 2 O 9 , the electric polarization in the magnetic ordered phases was clearly observed from the pyroelectric current measurements, which indicates its coexistence of magnetic ordering and ferroelectricity.  more » « less
Award ID(s):
2003117
NSF-PAR ID:
10417692
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
ECS Journal of Solid State Science and Technology
Volume:
11
Issue:
6
ISSN:
2162-8769
Page Range / eLocation ID:
063004
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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