Change of the energy loss of relativistic heavy ions in a gadolinium target at and above the ferromagnetic Curie temperature

The energy loss dE of 250 A MeV (∼52 GeV) bismuth ions in a 1 g/cm2 poly-crystalline gadolinium target was measured with the high-resolving magnetic spectrometer FRS at GSI as a function of the target temperature T at and above the Curie temperature TC of about 19 °C.After subtraction of effects due to thermal expansion of the target and due to a small asymmetric change of the charge state distribution, the relative energy-loss change (δE/dE)corr increases between 5 °C and 98 °C from 0 to 1.1(5) × 10−3. Between 13 °C and 15 °C a sharp increase by 0.26(3) × 10−3 is observed.