Possible role of phase segregation in the disagreement between the metal-insulator and ferromagnetic transition temperatures in some colossal magnetoresistance compounds
Abstract
The isovalent substitution of Gd for La in La0.7Ca0.3MnO3 lowers the paramagnetic-ferromagnetic transition temperature Tc and metal-insulator transition temperature TMI with a substantial increase in the electrical resistivity ρ. Reduction of the ferromagnetic saturation moment M (5 K) below that expected for complete ferromagnetic alignment of the Mn magnetic moments occurs and TMI is significantly lower than Tc for x>0.2. The observations are consistent with the existence of a granular mixture of ferromagnetic/conducting La-Ca-Mn-O and ferrimagnetic/insulating Gd-Ca-Mn-O. The ionic radius of the substituted rare-earth ion is found to be an important factor in determining whether or not granular behavior occurs. The results provide insight into why Tc≠TMI in some colossal magnetoresistance oxides.
- Publication:
-
Physical Review B
- Pub Date:
- May 2001
- DOI:
- 10.1103/PhysRevB.63.174436
- Bibcode:
- 2001PhRvB..63q4436T
- Keywords:
-
- 75.30.Vn;
- 75.50.Pp;
- 72.80.Ga;
- Magnetic semiconductors;
- Transition-metal compounds