Experimental verification of random-field critical and multicritical behavior

The existence of novel random-field critical and multicritical behavior in antiferromagnetic GdAlO3:2.75% La was verified. In the neighborhood of the bictritical point, the two second-order transition lines are described each by a different shift exponent, and a random-field crossover exponent RF=1.790.04 is deduced. At the random-field critical points, the specific-heat exponent crosses over to a value <-1, whereas at random-exchange critical points remains close to 0. © 1980 The American Physical Society.