Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
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116 <strong>Biennial</strong> <strong>Report</strong> <strong>2005</strong>-0727 K, following zero field cooled (ZFC) and field cooled (FC) process. In ZFC process, the sampleat 2 K is subsequently followed by magnetic field on and <strong>of</strong>f sequences, whereas in FC processthe cooling field is made <strong>of</strong>f during measurement <strong>of</strong> remanent magnetization as a function <strong>of</strong> time.The experiments suggest an unconventional relaxation behaviour in the system, as an effect <strong>of</strong>increasing surface exchange anisotropy with decreasing the size <strong>of</strong> antiferromagnetic nanoparticles.Unconventional relaxation in AFM CoRh 2 O 4 nano particlesRN Bhowmik, R RanganathanECMP4.1.1.26 Lattice expansion and non-collinear to collinear ferrimagnetic order inMnCr 2 O 4 nanoparticleWe have investigated the magnetic behavior <strong>of</strong> a typical spinel oxide MnCr 2 O 4 . Bulk sampleshows a sequence <strong>of</strong> magnetic states, which follows paramagnetic (PM) to collinear ferrimagnetic(FM)state below T c 45 K and collinear FM state to non-collinear FM state below T s 18 K. Thenanomaterial, prepared by mechanical milling <strong>of</strong> bulk sample, shows a systematic lattice expansionwith decreasing particle size. The magnetic measurement shows that both long-range ferrimagneticorder and the non-collinear spin structure are strongly modified in nanoparticles. For example, thesharp magnetic transition at T s is gradually disappeared for nanoparticles. The system also showssuper paramagnetic behavior for smaller particles. The decrease <strong>of</strong> spontaneous magnetization withdecrease <strong>of</strong> particle size may, according to the core-shell model for ferrimagnetic nanoparticle, bethe disorder effects <strong>of</strong> nanoparticles. However, the increase <strong>of</strong> Ts, and systematic increase <strong>of</strong> Blochexponent with decreasing particle size seems to be unusual. The present work highlights the effect<strong>of</strong> lattice expansion on unusual magnetism in MnCr 2 O 4 nanoparticles.RN Bhowmik, R Ranganathan, R NagarajanECMP4.1.1.27 Structural and magnetic studies on spark plasma sintered SmCo5/Fe bulknanocomposite magnetsSmCo5 + x wt.% Fe (x =0, 5 and 10) nanocomposite powders were synthesized by mechanicalmilling and were consolidated into bulk shape by spark plasma sintering (SPS) technique. Theevolution <strong>of</strong> structure and magnetic properties were systematically investigated in milled powdersas well as in SPS samples. A maximum coercivity <strong>of</strong> 8.9kOe was achieved in spark plasma
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