Regenerator material for extremely low temperatures and regenerator for extremely low temperatures using the same

摘要

A regenerator material for extremely low temperatures which comprises magnetic regenerator particles in which a rate of particles, which are fractured when a compressive stress of 5 Mpa is applied thereto using a die for mechanical strength evaluation, is not more than 1 wt.%. In this magnetic regenerator particles, a rate of magnetic regenerator particles having more than 1.5 form factor R expressed by L2/4 pi A, wherein L represents a perimeter of a projected image of each magnetic regenerator particle, and A represents an area of the projected image, is not more than 5%. Such a regenerator material for extremely low temperatures is capable of providing excellent mechanical properties for mechanical vibration with a high reproducibility. A regenerator for extremely low temperatures is formed by filling a regenerator container with a regenerator material for extremely low temperatures comprising the above-mentioned magnetic regenerator particles. Such a regenerator for extremely low temperatures can show excellent refrigerating performance for a long period of time. IMAGE