Volume 108, Number 1, October 2014
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||08 October 2014|
Spin-glass–like ground state and observation of exchange bias in Mn0.8Fe0.2NiGe alloy
1 UGC-DAE Consortium for Scientific Research, Kolkata Centre, Sector III, LB-8 Salt Lake, Kolkata 700 098, India
2 Department of Solid State Physics, Indian Association for the Cultivation of Science 2 A & B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, India
3 UGC-DAE Consortium for Scientific Research, University Campus - Khandwa Road, Indore 452 017, India
Received: 1 May 2014
Accepted: 23 September 2014
The ground-state magnetic properties of a hexagonal equiatomic alloy of nominal composition Mn0.8Fe0.2NiGe were investigated through dc magnetization and heat capacity measurements. The alloy undergoes a first-order martensitic transition below 140 K with simultaneous development of long-range ferromagnetic ordering from the high-temperature paramagnetic phase. The undoped compound MnNiGe has an antiferromagnetic ground state and it shows martensitic-like structural instability well above room temperature. Fe doping at the Mn site not only brings down the martensitic transition temperature, but it also induces ferromagnetism in the sample. Our study brings out two important aspects regarding the sample, namley i) the observation of exchange bias at low temperature, and ii) spin-glass–like ground state which prevails below the martensitic and magnetic transition points. In addition to the observed usual relaxation behavior, the spin glass state is confirmed by the zero-field–cooled memory experiment, thereby indicating cooperative freezing of spin and/or spin clusters rather than uncorrelated dynamics of superparamagnetic-like spin clusters. We believe that doping disorder can give rise to some islands of antiferromagnetic clusters in the otherwise ferromagnetic background which can produce interfacial frustration and exchange pinning responsible for spin glass and exchange bias effect. A comparison is made with doped rare-earth manganites where a similar phase separation can lead to a glassy ground state.
PACS: 75.50.Lk – Spin glasses and other random magnets / 75.47.Np – Metals and alloys / 81.30.Kf – Martensitic transformations
© EPLA, 2014
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