EXCHANGE ENERGY IN BCC HE-3

Values of the exchange energy J for bcc He3 have been obtained from the exchange contribution to the pressure in measurements extending to 13 mK. The relation between the exchange energy and the pressure is developed. A brief outline of the experimental arrangement including a description of a simple procedure for obtaining He3 of fairly high purity is given. The data analysis and uncertainty in J are discussed. Values of |J| are given and compared with other determinations. It is found for the solid near melting (V=24.1 cm3/mole), that |J|k=0.72 mK, with a strong volume dependence ln|J|lnV18. Assuming antiferromagnetic ordering, the Néel temperature for the solid near melting would be TN=2.0 mK. The specific heat, entropy, and thermal expansion of the solid are considered. A brief comment concerning He4 impurities is made. © 1969 The American Physical Society.