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Spectroscopic and Magnetic Investigations of Spin-frustrated Mn-Doped CoAl2O4 Spinel

Abstract

Single-phase polycrystalline spin-frustrated spinel oxides Co1−xMnxAl2O4 (0 ≤ x ≤ 0.3) have been prepared to investigate optical and magnetic properties. Linear variation of lattice parameter along with the characteristic hyperfine electron paramagnetic resonance (EPR) signal establishes the fact that the Mn2+ ions are incorporated at Co2+ sites of CoAl2O4 lattice. Optical absorption spectra reveal three absorption features in wavelength region: 250-400 nm, 500-700 nm and 1000-1700 nm. Optical band gap associated with the d-d transitions increases from 1.84 eV to 1.88 eV with 30% Mn substitution. Temperature dependent magnetization measurements indicate a clear transformation of magnetic ground state from collinear antiferromagnetic state (for x = 0) to spin-glass-like state (for x = 0.1), to cluster-glass-like state (for x = 0.2 and 0.3) with the increase of Mn concentration. In addition, our time dependent isothermal remanent magnetization (IRM) study further fortifies the above transformation of magnetic ground state. The value of magnetic frustration parameter moderately decreases with Mn substitution; but, the compositional variation is not monotonous.

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Publication details

The article was received on 19 Nov 2018, accepted on 05 Dec 2018 and first published on 07 Dec 2018


Article type: Paper
DOI: 10.1039/C8CP07140C
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Spectroscopic and Magnetic Investigations of Spin-frustrated Mn-Doped CoAl2O4 Spinel

    S. K. Pradhan, B. Dalal, A. Sarkar and S. K. K. De, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP07140C

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