||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,T-C is driven down to the mK range by alloying Ce-ligands (x), clear changes in the magnetic phase are observed once T-N,T-C < 2K. On the contrary, when T-N vanishes at finite temperature (driven by pressure or x) the phase boundaries do not reach temperatures lower than approximate to 3 K. In a third type of phase diagrams, characterized by a weak TN(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. (c) 2007 Elsevier B.V. All rights reserved.