Spin-Photonic, Photonic and other Relevant Properties ofNi2MnGe and Other Heusler Alloys

Various physical properties for ¯lms of Heusler alloys, such as Ni2MnGe and Cu2MnAl, with different atomic orders were studied. The films were deposited on glass substrates at several sub-strate temperatures from 150 to 730 K. The structural characterization was performed by using X-ray diffraction. A superconducting-quantum-interference-device magnetometer was employed to measure the temperature dependence of the spin properties. The photonic and the spin-photonic properties were also investigated. Alloy films with corresponding L21-type structural orders were successfully fabricated. The ordered films exhibited physical properties close to those of the cor-responding bulk alloy. The significant effects of structural disorder on the photonic, the spin, and the spin-photonic properties were experimentally observed. Unexpectedly, the disordered Ni2MnGe alloy films were not ferromagnetically ordered. Atomic disordering led to the disappearance of the high-energy absorption peak in the optical-conductivity spectrum and to the lack of a spin-photonic response. All these results were further analyzed in connection with the electronic structures of the alloy.