Cationic distribution, exchange interactions, and relaxation dynamics in Zn-diluted MnCo 2 O 4 nanostructures

Pramanik, P and Joshi, DC and Tiwari, N and Sarkar, T and Pittala, S and Salman, OO and Manga, MM and Thota, S (2019) Cationic distribution, exchange interactions, and relaxation dynamics in Zn-diluted MnCo 2 O 4 nanostructures. In: Journal of Applied Physics, 125 (12).

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Abstract

We report an experimental investigation of the electronic structure and magnetic properties of bulk and nanosized MnCo 2 O 4 diluted with Zn. The cationic distribution for tetrahedral A-site dilution is (Co 1-y A2 +Zn yA 2+ ) A Mn 3+ Co 3+ B O 4 ± δ, whereas B-site dilution results in (Co 2+ ) A Mn 1-xB 3+ Zn xB 2+ Co 3+ B O 4-δ . The strength of exchange interaction J ij between the magnetic ions in a bulk spinel lattice decreases by � 15 % for A-site dilution relative to the undiluted compound; however, B-site dilution results in an enhancement in J ij by 17%. The frequency and temperature dependence of dynamic-susceptibility � ac (f,T) studies of nanostructured compounds reveals the existence of spin-glass like behavior below the freezing temperature T F � 125.7K (for x B = 0.2) and 154.3 K (y A = 0.1). Relaxation time � follows the Power-Law variation with a dynamical critical exponent z ν = 6.17 and microscopic spin relaxation time � 0 = 4.4 � 10 -15 s for x B = 0.2 (for y A = 0.1, z ν = 5.2 and � o = 5.4 � 10 -13 s ). The amplitude and peak position in � ac (T) decreases with an increase in the DC bias field, which indicates that the spin-glass phase can survive in the presence of low fields forming a critical line with an exponent 2/3. This behavior is similar to the de Almeida-Thouless (AT-line) analysis in the T-H phase diagram which supports the existence of spin-glass like behavior below T F in these Zn diluted spinels. © 2019 Author(s).

Item Type:	Journal Article
Publication:	Journal of Applied Physics
Publisher:	American Institute of Physics Inc.
Additional Information:	Copyright for this article belongs to American Institute of Physics Inc.
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	06 May 2019 17:24
Last Modified:	06 May 2019 17:24
URI:	http://eprints.iisc.ac.in/id/eprint/62214

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