Browsing by Author "Chandrasekhar, K. Devi"

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Anisotropic spin-flip-induced multiferroic behavior in kagome Cu3Bi(SeO3)(2)O2Cl
(2017-03-15)
Wu, H. C.
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Chandrasekhar, K. Devi
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Yuan, J. K.
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Huang, J. R.
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Lin, J. -Y.
Compared to the previous report on Cu3Bi(SeO3)(2)O2X (X = Cl, Br) [V. Gnezdilov et al., (arXiv: 1604.04249)], where no dielectric anomaly was observed without magnetic field near T-N similar to 25.6K, we further present the dielectric behaviors without and with magnetic field in Cu3Bi(SeO3)(2)O2Cl. At zero field H = 0, an antiferromagnetic transition from magnetization and specific heat measurements is clearly established at T-N, while no dielectric anomaly was observed. Those results are similar to the previous report [V. Gnezdilov et al., (arXiv: 1604.04249)]. Above the critical field H-c similar to 0.8 T, a metamagnetic spin-flip transition from antiferromagnetic to ferrimagnetic order at T similar to T-N is induced anisotropically only for H broken vertical bar broken vertical bar c. Meanwhile, a ferroelectric behavior from dielectric and pyroelectric current measurements is observed below T similar to T-N; then a corresponding type-II multiferroics emerges above H-c. The key mechanism of the anisotropic spin-flip-induced multiferroicity in Cu3Bi(SeO3)(2)O2Cl can be ascribed to the breaking of magnetic twofold symmetry in the bc plane above H-c.
Magnetostructural coupling and multiferroic properties in the spin-frustrated system Ni1-xZnxCr2O4
(2016-11-28)
Chandrasekhar, K. Devi
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Murthy, J. Krishna
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Lin, J. -Y.
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Wu, H. C.
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Tseng, W. J.
The magnetic phase diagram of Ni1-xZnxCr2O4 demonstrates complex magnetic transitions for x = 0.05 with two long-range magnetic- order transitions at T-C1 = 41K and T-C2 = 17 K. A glasslike feature emerges between TC1 and TC2 with the application of a direct current (dc) magnetic field in alternating current (ac) susceptibility measurements. Dielectric measurements show a change from the conventional dielectric to a quantum-paraelectric-like behavior without anomalies near the magnetic ordering temperature in the range 0.05 <= x <= 1. The strong correlation among magnetic, dielectric, and ferroelectric properties near the structural relaxation temperatures 41 and 17 K confirms the emergence of multiferroic behavior in Ni0.95Zn0.05Cr2O4. A significant x-ray magnetic circular dichroism signal at the Ni site and ac susceptibility measurements indicate a spin-canting behavior between TC1 and TC2. The dilute doping of the non-Jahn-Teller Zn ion in the Jahn-Teller Ni site modulate the different magnetic exchange interactions of Ni and Cr, which could invoke spin-canting and multiferroic behaviors.
Observation of oscillation like magnetocaloric effect in multiferroic Ni0.95Zn0.05Cr2O4
(2019-01-15)
Chandrasekhar, K. Devi
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Murthy, J. Krishna
;
Lin, J-Y
;
Wu, H. C.
;
Yang, H. D.
In this study, the magnetic and magnetocaloric effects of Ni0.95Zn0.05Cr2O4 have been investigated systematically. The distinct magnetic phases in different temperature zones were identified using a combined analysis of Arrott plots and virgin magnetization curves. The magnetocaloric phenomenon is sensitive to the spin correlation of the nickel and chromium magnetic sublattices within each distinct temperature zone, as is reflected by the modulation of the magnetocaloric sign. This unique oscillatory like magnetocaloric effect within the multiferroic phase may indicate the possibility of a multicaloric effect in Ni0.95Zn0.05Cr2O4. (C) 2018 Elsevier B.V. All rights reserved.