Magnetic, thermal and transport behavior in single crystalline RCu2Ge2 (R=La, Ce, Pr and Sm) compounds

Magnetic behavior of single crystalline RCu2Ge2 (R=La, Ce, Pr and Sm) compounds is reported. Single crystals were grown using Cu-Ge flux. The compounds crystallize in a tetragonal structure with space group I4/mmm. LaCu2Ge2 shows a diamagnetic behavior. CeCu2Ge2, PrCu2Ge2 and SmCu2Ge2 orders antiferromagnetically at ≈4.2, 15 and 14.5 K respectively with [001] as the easy axis of magnetization. CeCu2Ge2 shows a Kondo behavior. The Kondo temperature TK, calculated using two different models is of order of 5 K. In PrCu2Ge2, an additional magnetic transition is observed below 4 K. The origin of the magnetic behavior is attributed to magnetoelastic effects. A possibility of change in easy axis of magnetization after field cycling (below 4 K) is discussed and such effect is rarely observed. The magnetic and specific heat behavior of CeCu2Ge2 and PrCu2Ge2 are analyzed on the basis of crystalline electric field (CEF) model. The CEF splited ground state of rare earth ions is calculated. The magnetic isotherm of SmCu2Ge2 exhibits de Haas-van Alphen oscillations. It is inferred from the frequency spectrum analysis that, the Fermi surface cross-section along [001] is large compared to [100].