Hyperfine Enhanced Nuclear Magnetic Cooling in Van Vleck Paramagnetic Intermetallic Compounds

Abstract

In strongly Van Vleck paramagnetic rare-earth alloys or compounds, large hyperfine fields can be induced at the rare-earth nucleus with moderate external fields. These fields are useful to generate low temperatures by the method of nuclear adiabatic demagnetization. Experiments in the Van Vleck paramagnets PrPt5 and PrTl3 are described in which end temperatures of 3.5 and 1.5 mK are obtained starting from about 60 mK and 20 kOe. The possibility of nuclear ferromagnetism in PrTl3 is discussed and compared with observations.