μSR studies of the electron-doped Ca1-xSmxMnO3

We have performed muon spin relaxation (μSR) experiments on undoped CaMnO3 and electron-doped Ca1-xSmxMnO3 for x=0.1,0.15 and 0.3. Undoped CaMnO3 is a G-type antiferromagnet with a Néel temperature of TN≈122K. The μSR signal shows three well-defined frequencies, which decrease continuously with temperature and becomes zero at TN≈122K. The electron-doped Ca0.85Sm0.15MnO3 which shows colossal magnetoresistive (CMR) behaviour, undergoes a structural and magnetic transition at Tc≈125K. The μSR signal shows heavily damped oscillating signal. The frequency decreases continuously with increasing temperature. Ca0.9Sm0.1MnO3 and Ca0.7 Sm0.3MnO3 show only relaxation and do not show any frequency. We have determined temperature variation of the muon relaxation rates below and above the magnetic and charge order transitions under zero and longitudinal magnetic fields, which give important information about the nature of these transitions.