Detailed investigation of the magnetic phase diagram of CeRu2Ge2 up to 11 GPa

The electrical resistivity p(T) and transverse magnetoresistivity of magnet ically ordered CeRu2Ge2 (TN = 8.55 K and T-c= 7.40 K) was measured as a fun ction of pressure up to P = 11 GPa and down to T = 30 mK. Pressure first in creases TN and suppresses T,. Then a second transition, corresponding proba bly to a modification of the AFM state, appears at T-L<T-N in the pressure range 3.5<P<7.2 GPa. The long-range magnetic order disappears at a critical pressure P-c= 8.7 GPa like T(N)proportional to(P-c- P)(m), with m = 0.71(8 ). The p(T) curves at low temperature and low pressure (P<7.8 GPa) are well described by a power law rho(T) proportional to T-n, with exponents n>2. W ell above P,, a Fermi liquid behavior (n =2) is observed and the A coeffici ent of the quadratic T dependence decreases with pressure. In the pressure interval P-c+/-0.8 GPa, exponents close to n =1.5 indicate a deviation from a Fermi liquid description. The magnetoresistivity curves show different a nomalies at characteristic magnetic fields B-a, B-c, and B-M. The latter oc curs close to P, and is reminiscent of the metamagneticlike field in CeRu2S i2. A quantitative comparison between the (T,P) data of CeRu2Ge2 and the (T ,x) data of CeRu2(Si1-xGex)(2) on the basis of the unit-cell volume as the crucial parameter shows that the same (T,V) diagram is obtained.