Abstract
Insulator-metal phenomena depending on band filling (doping degree), temperature, and external magnetic field have been investigated for prototypical double-exchange ferromagnets, namely, crystals of (0≤x≤0.6). The electronic phase diagram in the plane of the temperature vs nominal hole concentration (x) has been deduced from the magnetic and electrical measurements on the melt-grown crystals. Around the ferromagnetic transition temperature , large negative magnetoresistance was observed. Irrespective of temperature, reduction of the resistivity is scaled with the field-induced magnetization (M) as -Δρ/ρ=C(M/ for M/≲0.3, where is the saturated magnetization. The coefficient C strongly depends on x, i.e., C≊4 near the compositional insulator-metal phase boundary (∼0.17), but decreases down to ≊1 for x>=0.4, indicating the critical change of the electronic state.
- Received 20 January 1995
DOI:https://doi.org/10.1103/PhysRevB.51.14103
©1995 American Physical Society