Nippon Steel Corporation

Japan Science and Technology Agency

Takashi Fukuda

Tomoyuki Kakeshita

Noriyuki Negi

Tatsuo Nagata

Koji Moriguchi

Sukeyoshi Yamamoto

Mitsuharu Yonemura

Tomoyuki Terai

Tetsuya Takeuchi

Provided is a negative electrode active material that can improve the capacity per volume and charge-discharge cycle characteristics of a nonaqueous electrolyte secondary battery represented by a lithium ion secondary battery. The negative electrode active material according to the present embodiment contains an alloy phase. The alloy phase undergoes thermoelastic diffusionless transformation when releasing or occluding metal ions. The negative electrode active material of the present embodiment is used in a nonaqueous electrolyte secondary battery. Thermoelastic diffusionless transformation refers to so-called thermoelastic martensitic transformation.

Negative electrode active material

The present invention provides a supermagnetostrictive alloy capable of providing a larger shift (lager magnetostriction) with excellent workability, which is applicable to an actuator in response to advances in downsizing of electronic devices and upgrading of medical instruments and production apparatuses. The supermagnetostrictive alloy has a degree of order of 0.6 to 0.95 achieved by subjecting Fe Pt (&minus;0.02&lE;&times;&lE;0.2) to a heat treatment. The present invention also provides a method for the preparation of a supermagnetostrictive alloy having a magnetostriction of 0.3% or more, particularly 0.5% or more, comprising the steps of subjecting the Fe Pt alloy of a raw material to a homogenization annealing, and then subjecting the resulting product to a heat treatment at 700 to 1000 K for 0.5 to 600 hours.

Supermagnetostrictive alloy and method of preparation thereof

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Kusatsu, Japan

Takashi Fukuda