MAGNETIC THERMOMETRY TO BELOW ONE MILLIKELVIN WITH LANTHANUM-DILUTED CERIUM MAGNESIUM-NITRATE

Measurements are presented of the pressure and magnetic temperature coordinates of the phase diagram of liquid 3He using a powdered Ce0.05La0.95 magnesium nitrate thermometer in the shape of a right circular cylinder with diameter equal to height. The lowest magnetic temperature observed with the thermometer is 0.41 mK. The magnetic temperature of the intersection of the second-order line with the melting curve is 2.625 mK, and the critical temperature at zero pressure is 1.055 mK. The difference between Tc* and TAB* extrapolated to melting pressure is 0.57 mK, in excellent agreement with the difference TA-T′B found from measurements along the melting curve. The present data are compared with the La Jolla provisional absolute scale based on noise thermometry and zero sound. We make the assumption that the absolute temperature T and the present magnetic temperature T* are related by T = T* + Δ and use the resultant scale to reanalyze a variety of experimental results that had been given in terms of the La Jolla provisional scale. © 1979 Plenum Publishing Corporation.