Transport, magnetic, specific heat, internal friction, and shear modulus in the charge ordered La0.25Ca0.75MnO3 manganite

The resistivity, magnetization, specific heat, shear modulus, and internal friction in the charge-ordered (CO) La0.25Ca0.75MnO3 were studied. The electronic conduction in the CO state was found to obey Mott's variable-range hopping model with a change in the localization length xi near T-N. A large decrease of the magnetization was observed between the Neer temperature T-N and the charge ordering transition temperature T-CO, which was attributed to the consequence of the orbital ordering. Drastic stiffening in shear modulus and an internal friction peak appeared just below T-CO, and were explained as due to the coupling between the lattice strain and the orbital degree of freedom. A small upturn of the magnetization and a small softening of the ultrasound near T(CA)approximate to42 K suggest the evolution of spin canting from the matrix of long-range antiferromagnetic state. (C) 2003 American Institute of Physics.