Crossover from classical to quantum regime in Ce-lattice systems

Different types of magnetic phase diagrams are analyzed with the scope to detect signs of a crossover between the classical (thermal fluctuations) regime and the critical (quantum fluctuations) one. In systems where T N , C is driven down to the mK range by alloying Ce-ligands ( x), clear changes in the magnetic phase are observed once T N , C < 2 K . On the contrary, when T N vanishes at finite temperature (driven by pressure or x) the phase boundaries do not reach temperatures lower than ≈ 3 K . In a third type of phase diagrams, characterized by a weak T N ( x , p ) dependence, signs of phase separation are suspected. Distinctive properties of each mentioned group are recognized and some exemplary cases analyzed in detail. Those properties coincide indicating a crossover temperature slightly above 2 K.