Minoru Takahashi1, Terunobu Miyazaki1, Fumihisa Ono2 and Keiichi Takakura1
1Department of Applied Physics, Faculty of Engineering, Tohoku University, Sendai
An experimental study of the annealing effect upon the magnetic properties such as hysteresis loop and domain structure and also upon electrical resistivity and X-ray diffraction pattern has been carried out for rapidly quenched Fe80P13C7 amorphous alloy.
The results are summarized as follows: (1) With increasing annealing temperature, a square-shaped hysteresis loop with Hc\fallingdotseq0.07∼0.13 Oe in the rapidly quenched state becomes declined and the Hc slightly decreases to take a minimum of 0.04 Oe on annealing at around 350°C. However, Hc abruptly increases up to 120∼150 Oe after annealing at about 420°C, the crystallization temperature. (2) The fingerprint-type domain observed in the quenched state becomes smaller and when annealed below about 300°C, its pattern changes from a maze to a 180°ree domain through the stripe domains. After annealing at around 400°C, the 180°ree domain disappears. (3) The electrical resistivity increases from 160 to 210 μ \varOmega⋅cm, reaches a broad maximum (220∼250 μ \varOmega⋅cm) after annealed near 300∼350°C and then decreases to a constant value of 120 μ \varOmega⋅cm beyond 500°C. (4) The halo pattern observed in the quenched state does not show any change with annealing below about 400°C. When it is annealed in the vicinity of the crystallization temperature, the diffraction lines corresponding to α -Fe and Fe3P appear first and then those for Fe3C appear with a further increase in temperature.
The reason for the low coercive force in the amorphous state and its change with annealing below the crystallization temperature are discussed on the basis of the fluctuation model for the internal stress caused by the rapid quenching. The high Hc after the crystallization is also discussed in terms of the shape anisotropy of the precipitating crystallites of α -Fe and Fe3P alloys in the matrix of a highly strained state of Fe-P-C alloy.
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