The martensitic transition, magnetocaloric effect (MCE) and shape memory effect (MSE) of ferromagnetic Heusler alloys Ni50Mn50−xSbx (x = 12, 13 and 14) have been investigated. A large positive magnetic entropy change ΔSM was observed in the vicinity of the martensitic transition. The maximum value of ΔSM is 9.1 J kg−1 K−1 in Ni50Mn37Sb13 at 287 K for a magnetic field change of 5 T. This change originates from the first-order transition from a low-temperature weak-magnetic martensitic phase to a high-temperature ferromagnetic parent phase. A magnetic-field-induced shape recovery strain of about 15 ppm at room temperature and at a relatively low magnetic field (1.2 T) was observed to accompany the reverse martensitic transformation. The large field-induced MCE and MSE in the NiMnSb system make it a promising material for room-temperature application.

Shell-core structures of Fe(C), Co(C) and Fe-Co(C) nanocapsules, prepared by an arc discharge process in a mixture of methane and helium, have been demonstrated by means of high-resolution transmission electron microscopy (HRTEM). These nanoscale magnetic cores are protected by graphite shells. It has been found that the zero-field-cooled (ZFC) magnetization of Fe-Co(C) nanocapsules that display different characteristics in three temperature ranges can be well interpreted in terms of the unblocking of magnetization of small single-domain particles and the depinning of large multidomain particles. The saturation magnetization of these nanocapsules decreases monotonically, while the coercivity decreases significantly with increasing temperature.

The influence of a partial boron substitution on the crystal structure, Curie temperature, easy magnetization direction and magnetostriction of Tb0.7Pr0.3Fe2 has been studied. The matrix of Tb0.7Pr0.3Fe2 consists of the (Tb, Pr)Fe2 phase with a cubic MgCu2-type structure coexisting with a large amount of the (Tb, Pr)Fe3 phase with a rhombohedral PuNi3-type structure. The introduction of boron can effectively restrain the emergence of the iron-rich phase and thus the Tb0.7Pr0.3(Fe1-xBx)2 alloys are essentially single phase compared with the boron free material. The linear magnetostriction at room temperature λa = λ∥-λ⊥ and TC pronouncedly increase with the boron substitution.

The decomposition of pyrolytic boron nitride (p-BN) during milling is studied as a function of the milling time. It has been found that the p-BN compound can be partially decomposed by milling until an amorphous p-BN phase is formed so that the content of nitrogen in the p-BN system will not continue to be changed by the milling process. Furthermore, the structure and magnetic properties of Nd2Fe14BNx-based alloys prepared by mechanical alloying using either p-BN or milled p-BN as starting material have been investigated. The Nd2Fe14BNx phase with x up to 0.25 coexists with some amounts of NdN, the Nd-rich phase and -Fe. A pre-milling process of p-BN favours the formation of the Nd2Fe14BNx phase. The magnetic properties of Nd16Fe76B8Nx alloys prepared by using milled p-BN are better than those made of non-milled p-BN. The Curie temperature of the Nd2Fe14BN0.25 phase is 335 °C, which is slightly higher than that of the Nd2Fe14B compound. A coercivity higher than 20 kOe is achieved for Nd2Fe14BNx-based alloys by adding excess Nd, which is close to the value of Nd16Fe76B8 prepared by using pure B.

Exchange bias (EB) and magnetic properties of ferrimagnetic (FI) Fe3O4 and antiferromagnetic (AFM) Cr2O3 nanocomposites prepared by mechanical alloying have been investigated. A large EB field of 2.2 kOe at 10 K is observed in one of the nanocomposites, which may be related to the uncompensated and pinned AFM spins at the interface between FI and AFM phases of the nanocomposites. The EB field varies with the strength of cooling field and the content of the Cr2O3 phase, the phenomena observed are explained in terms of interfacial exchange interaction between the two phases.