Magnetic polarons in antiferromagnetic CaMnO3-x (x<0.01) probed by O17 NMR
Abstract
We study with O17 NMR and bulk magnetization a lightly electron doped CaMnO3-x (x<0.01) polycrystalline sample in the G -type antiferromagnetic state. The O17 NMR spectra show two lines with very different intensities corresponding to oxygen sites with very different local magnetic environments. The more intense unshifted line is due to the antiferromagnetic (AF) matrix. The thermal dependence of the magnetic moment of the AF sublattice deduced from the O17 linewidth is typical of insulating three-dimensional Heisenberg antiferromagnets. The less intense, strongly shifted line directly evidences the existence of ferromagnetic (FM) domains embedded in the AF spin lattice. The extremely narrow line in zero magnetic field indicates a nearly perfect alignment of the manganese spins in the FM domains which also display an unusually weak temperature dependence of their magnetic moment. We show that these FM entities start to move above 40 K in a slow-diffusion regime. These static and dynamic properties bear a strong similarity with those of a small size self-trapped magnetic polaron.
- Publication:
-
Physical Review B
- Pub Date:
- June 2009
- DOI:
- 10.1103/PhysRevB.79.214414
- Bibcode:
- 2009PhRvB..79u4414T
- Keywords:
-
- 75.25.+z;
- 75.47.Lx;
- 76.60.Es;
- 76.60.Jx;
- Spin arrangements in magnetically ordered materials;
- Manganites;
- Relaxation effects;
- Effects of internal magnetic fields