Synthesis, Optical, and Magnetic Properties of BaNiF Nanowires.

A low-temperature hydrothermal route has been developed, and pure phase BaNiF nanowires have been successfully prepared under optimized conditions. Under the 325 nm excitation, the BaNiF nanowires exhibit three emission bands with peak positions locating at 360, 530, and 700 nm, respectively. Combined with the first-principles calculations, the photoluminescence property can be explained by the electron transitions between the t and e orbitals. Clear hysteresis loops observed below the temperature of 60 K demonstrates the weak ferromagnetism in BaNiF nanowires, which has been attributed to the surface strain of nanowires. Exchange bias with blocking temperature of 55 K has been observed, which originates from the magnetization pinning under the cooling field due to antiferromagnetic core/weak ferromagnetic shell structure of BaNiF nanowires.