S.C. Ma

Large exchange bias field in the Ni–Mn–Sn Heusler alloys with high content of Mn

The exchange bias properties have been investigated in bulk Mn50Ni40−xSn10+x (x=0, 0.5, and 1) Heusler alloys with high content of Mn, in which the largest exchange bias field is up to 910 Oe for Mn50Ni40Sn10 alloy. In these alloys, the excess Mn atoms would occupy not only the Sn sites but also the Ni sites, and the moments of Mn on Sn or Ni sites are coupled antiferromagnetically to those on the regular Mn sites, respectively. The origin of this considerably large exchange bias field has been discussed.

The magnetostructural transformation and magnetocaloric effect in Co-doped MnNiGe1.05 alloys

A series of MnNi1−xCoxGe1.05 (x = 0, 0.03, 0.05, 0.07, 0.09, and 0.11) alloys were prepared by the arc-melting method. With increasing content of Co, a first-order magnetostructural transformation between the antiferromagnetic TiNiSi-type phase and the ferromagnetic Ni2In-type phase was observed. A magnetic and crystallographic phase diagram for MnNi1−xCoxGe1.05 alloys was proposed in this paper. Owing to the abrupt and large jump of magnetization around the magnetostructural transformation, MnNi1−xCoxGe1.05 (x = 0.07, 0.09, 0.11) alloys show large and positive magnetic entropy changes at relatively low field.

The martensitic transformation, magnetocaloric effect, and magnetoresistance in high-Mn content Mn47+xNi43−xSn10 ferromagnetic shape memory alloys

A series of high-Mn content Mn47+xNi43−xSn10 (x=0, 1, 2, 3, 4, and 5) ferromagnetic shape memory alloys were prepared by arc melting method. The martensitic transformation were observed in these alloys, even the content of Mn is higher than 50 at. %. The phase transition temperature of these alloys can be adjusted by tuning the compositions of Ni and Mn. Large positive magnetic entropy change and negative magnetoresistance which originate from the magnetic-field-induced martensitic transformation are obtained in these alloys.

Investigation of the intermediate phase and magnetocaloric properties in high-pressure annealing Ni–Mn–Co–Sn alloy

The Ni–Mn–Co–Sn alloy is prepared by high-pressure annealing method. Besides the enhanced martensitic transformation temperature and the Curie temperature of austenite, an intermediate phase above the martensitic transformation is observed in this alloy. As a result, two successive magnetic entropy changes with the same sign are obtained around room-temperature, corresponding to the martensitic transformation and intermediate phase transition, respectively. The origin of the intermediate phase for high-pressure annealing Ni–Mn–Co–Sn alloy is discussed.

Large converse magnetoelectric effect in Metglas FeCoBSi and 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 laminated composite

Converse magnetoelectric (CME) effect is investigated in a FeCoBSi/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 laminated composite by using induction method within different frequencies. A large CME coefficient of 3.05 G/V is observed at the resonance frequency of 76.5 kHz under a low bias magnetic field of 50 Oe. The CME coefficient of the heterostructure is almost constant and exhibits a relatively high value in a wide frequency span of 1–64 kHz. The origin of large CME effect and the advantages of Metglas acting as ferromagnetic layer are discussed in the present paper.

Large and highly reversible magnetic field-induced strains in textured Co1−xNixMnSi alloys at room temperature

The metamagnetic transition and magnetoelastic properties are investigated in transition-metal-based Co1?xNixMnSi (0 < x < 0.03) alloys. Large low-field magnetostrains are observed in the Ni-doped CoMnSi alloys. Compared with some other metamagnetic materials with large magnetic field-induced strains, the present alloys show highly reversible magnetoelastic behaviour and have almost constant strain outputs around room temperature. These observations may shed light on developing transition-metal-based magnetostrictive materials.

A Review on the Regulation of Magnetic Transitions and the Related Magnetocaloric Properties in Ni-Mn-Co-Sn Alloys

In Ni-Mn-X (X =In, Sn, Sb) ferromagnetic shape memory alloys, a ferromagnetic transition from paramagnetic to ferromagnetic austenite and a martensitic transformation from ferromagnetic austenite to weak magnetic martensite occur in some particular composition ranges, in which abundant physical properties have been observed by the abrupt change of magnetization and resistivity around their transition temperatures in these alloys. Therefore, tuning the martensitic transformation temperature (TM) and enlarging the working-temperature interval for Ni-Mn-X (X=In, Sn, Sb) alloys, are of great importance. In the present paper, we will focus on the effect of external factors, including pre-deformation, annealing, and high pressure annealing, on the magnetic transitions and the related magnetocaloric properties in Ni-Mn-Co-Sn ferromagnetic shape memory alloys. Our approaches and the main results in this particular field will be reviewed.