Bhowmik, R. N. ; Ranganathan, R. ; Nagarajan, R. (2006) Lattice expansion and noncollinear to collinear ferrimagnetic order in a MnCr2O4 nanoparticle Physical Review B, 73 (14). 144413_1-144413 _9. ISSN 0163-1829
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Official URL: http://prb.aps.org/abstract/PRB/v73/i14/e144413
Related URL: http://dx.doi.org/10.1103/PhysRevB.73.144413
Abstract
We report the magnetic behavior of spinel chromite MnCr2O4. Bulk MnCr2O4 shows a sequence of magnetic states, i.e., paramagnetic (PM) to collinear ferrimagnetic (FM) state below TC~45 K and collinear FM state to noncollinear FM state below TS~18 K. Decrease of particle size reduces the noncollinear spin structure and consequently, magnetic transition at TS decreases in nanoparticle samples. However, ferrimagnetic order is still dominating in nanoparticles, except the observation of superparamagnetic-like blocking and decrease of spontaneous magnetization. This, according to the core-shell model of ferrimagnetic nanoparticles, may be due to surface disorder effects of nanoparticles. The system also shows the increase of TC in nanoparticle samples, which is not consistent with the core-shell model. The analysis of the M(T) data, applying spin wave theory, has shown an unusual Bloch exponent value 3.35 for bulk MnCr2O4, which decreases and approaches 1.5, a typical value for any standard ferromagnet, with decreasing particle size. We have also observed the lattice expansion in MnCr2O4 nanoparticles. The present work shows the correlation between a systematic increase of lattice parameter and the gradual decrease of B site noncollinear spin structure in MnCr2O4.
Item Type: | Article |
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Source: | Copyright of this article belongs to American Physical Society. |
ID Code: | 24185 |
Deposited On: | 29 Nov 2010 10:15 |
Last Modified: | 17 May 2016 07:55 |
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