Anomalous Hall effects in Co2FeSi Heusler compound films and Co2FeSi-Al2O3 granular films

作者：Qin Zhu; Liu Xin Dian; Li Zhi Qing^*

来源：Journal of Applied Physics, 2012, 111(8): 083919.

DOI：10.1063/1.4707846

We fabricated three Co2FeSi Heusler compound films at different temperatures (room temperature, 673, and 873 K) by rf sputtering deposition method and a series of (Co2FeSi)(x)(Al2O3)(1-x) (0.4 less than or similar to x less than or similar to 1) granular films at room temperature by co-sputtering method. The structures as well as the temperature behaviors of anomalous Hall resistivities, low-field Hall sensitivities, and longitudinal resistivities of those films were investigated experimentally. We found that the Co2FeSi Heusler compound film deposited at room temperature is poorly crystallized, the film deposited at 673 K is crystallized in the disordered A2 type structure, and L2(1) and B2 structures are present in the film deposited at 873 K. For the Co2FeSi films deposited at 673 and 873 K, the saturated anomalous Hall resistivity rho(s)(A) scales with the longitudinal resistivity rho(xx) as rho(s)(A) proportional to rho(n)(xx), with n much larger than 2. There is no scaling relation between rho(s)(A) and rho(xx) for the (Co2FeSi)(x)(Al2O3)(1-x) (0.58 <= x <= 1, x = 1 represents the Co2FeSi film deposited at room temperature) granular films. For the granular films, as x decreases from 1 to 0.67, the magnitude of rho(xx) increases by a factor of similar to 25, whereas the magnitude enhancement in rho(s)(A) is less than 50%, which strongly suggests that the longitudinal and anomalous Hall transports in ferromagnetic granular films are governed by different mechanisms. The low-field Hall sensitivities of (Co2FeSi)(x)(Al2O3)(1-x) films with x values of 0.6 and 0.65 are large and temperature insensitivity from 300 down to similar to 75 K, which might make them be good candidate materials for low-field Hall sensors.

• 出版日期2012-4-15
• 单位天津大学