[′hī·pər‚fīn in′hanst ¦nü·klē·ər ′kül·iŋ] (cryogenics) A version of adiabatic demagnetization in which a sample containing magnetic ions, embedded in a suitable crystal which quenches the hyperfine fields, is cooled in a moderate external field which reinduces the hyperfine fields, and is then thermally isolated and removed from the external field.