H. Morito, K. Oikawa, A. Fujita, R. Kainuma, K. Ishida, K. Fukamichi, Tohoku University, Sendai, Japan
To obtain a large strain for Ni-Fe-Ga ferromagnetic shape memory alloys (FSMAs), Co and Mn were added to increase Curie temperature and the magnetic-field-induced strain (MFIS) has been investigated under static stresses. It was found that magneto crystalline anisotropy constant K is increased by the addition of Co, and Ni49Fe18Ga27Co6 alloy shows a relatively large value of 1.2 × 106 erg/cm3 at 300 K. From the stress-strain curves for this alloy, the twinning stress is estimated to be 8 ~ 9 MPa. Consequently, the Ni49Fe18Ga27Co6 alloy exhibits a large MFIS of about 8.5 % at room temperature under a static compressive stress of about 8 MPa. The magnetic properties are effectively controlled by addition of Mn, and Ni49.5Fe14.5Mn4.0Ga26.0Co6.0 alloy exhibits a large MFIS of 11.3 % under a static stress. From these results, these alloy systems are promising practical FSMA systems with a large MFIS.
Summary: To obtain a large strain for Ni-Fe-Ga ferromagnetic shape memory alloys (FSMAs), Co and Mn were added to increase Curie temperature and the magnetic-field-induced strain (MFIS) has been investigated under static stresses. It was found that magneto crystalline anisotropy constant K is increased by the addition of Co, and Ni49Fe18Ga27Co6 alloy shows a relatively large value of 1.2 × 106 erg/cm3 at 300 K. From the stress-strain curves for this alloy, the twinning stress is estimated to be 8 ~ 9 MPa. Consequently, the Ni49Fe18Ga27Co6 alloy exhibits a large MFIS of about 8.5 % at room temperature under a static compressive stress of about 8 MPa. The magnetic properties are effectively controlled by addition of Mn, and Ni49.5Fe14.5Mn4.0Ga26.0Co6.0 alloy exhibits a large MFIS of 11.3 % under a static stress. From these results, these alloy systems are promising practical FSMA systems with a large MFIS.
