ORCID Profile
0000-0002-8569-8764
Current Organisation
Nanyang Technological University
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Publisher: AIP Publishing
Date: 15-08-2008
DOI: 10.1063/1.2973187
Abstract: Exchange bias phenomena are observed in the bulk polycrystalline Ni49.5Mn34.5In16 alloy in which ferromagnetic and antiferromagnetic phases coexist in the martensitic state. Both the exchange bias field and coercivity are strongly dependent on temperature. The training effect of the exchange bias is found to be very small in the present alloy and can be explained by the depinning of uncompensated antiferromagnet spins. These results suggest that the ferromagnetic and antiferromagnetic domains couple at the interfaces and as a result induce the exchange bias. Such behavior is an addition to the multifunctional properties of the Ni49.5Mn34.5In16 ferromagnetic shape memory alloy.
Publisher: Elsevier BV
Date: 03-2010
Publisher: AIP Publishing
Date: 15-01-2009
DOI: 10.1063/1.3068180
Abstract: A second-order ferromagnetic transition is observed in the martensitic state of Ni49.5Mn32.5Cu4Sn14 alloy and the critical behavior around the transition is investigated by dc magnetization measurements. With the help of modified Arrott plots, Kouvel–Fisher method, and Widom scaling relation, the values of TcM (ferromagnetic transition temperature in the martensite), and critical exponents: β (associated with the spontaneous magnetization), γ (relevant to the initial susceptibility), and δ (associated with the critical magnetization isotherm) are obtained. The scaling plots show that the obtained values of the critical exponents are reliable. The values of the critical exponents of Ni49.5Mn32.5Cu4Sn14 are different from those predicted by several theoretical models, i.e., mean-field theory, three-dimensional Heisenberg model, and three-dimensional Ising model. The magnetic interactions exhibit two different behaviors: long-range magnetic interaction below TcM and local magnetic interaction above TcM. The change in Mn moments may be responsible for the change in magnetic interactions around TcM.
Publisher: Informa UK Limited
Date: 21-01-2011
Publisher: Elsevier BV
Date: 07-2008
Publisher: American Physical Society (APS)
Date: 17-02-2011
Publisher: AIP Publishing
Date: 15-09-2009
DOI: 10.1063/1.3225578
Abstract: The thermal-history-dependent (THD) isothermal magnetoresistance (MR) behavior of Ni49.5Mn34.5In16 metamagnetic shape memory alloy is investigated. Irreversibility in isothermal MR is observed in reverse martensitic transformation temperature range, while an intriguing “overshooting” phenomenon is observed in forward martensitic transformation temperature range, showing a strong thermal-history dependence of MR behavior. Such a THD MR behavior can be explained in terms of phase coexistence, THD metastable phase, and magnetic-field-induced phase transition.
Publisher: AIP Publishing
Date: 15-02-2012
DOI: 10.1063/1.3686717
Abstract: We report a large unusual exchange bias effect occurred after zero-field cooling from an unmagnetized state (ZEB) in Ni-Mn-Sn alloys, in which the maximum ZEB field is about twice as large as that observed in Ni-Mn-In alloys at moderate field range (& 40 kOe). The ZEB field can be tuned by tuning the magnitude of the initial magnetization fields and its sign is strongly dependent on the direction of the initial magnetization fields. Furthermore, the ZEB effect only exists in alloys with volume fraction of superparamagnetic domains less than the percolation limitation in three-dimensional system (∼16%). The present results confirm the universality of this unusual ZEB effect and suggest that NiMn-based alloys provide a platform to obtain this unusual ZEB effect. Such ZEB effect may also exist in other systems with similar magnetic properties.
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