DIRECT DEMAGNETIZATION COOLING OF HIGH-DENSITY SOLID HE-3

Nuclear adiabatic demagnetization has been done for both hcp and bcc solid He-3 with exchange interactions of the order of 10 muK. Observed isochoric pressure increase during the demagnetization for the bcc sample at a molar volume of 19.99 cm3/mol showed clear magnetic transitions at the upper and the lower critical fields as is known for lower density solids. On the other hand, no pressure increase was observed for the hcp sample at 19.07 cm3/mol down to a zero magnetic field. These observations give strong evidence that the ground state in hcp He-3 is ferromagnetic.