Charge/orbital and antiferromagnetic ordering in LaSr2Mn2O7

Abstract First μSR results for the bilayered manganite LaSr 2 Mn 2 O 7 are reported. We have studied the effect on the relaxation rates of the charge/orbital and antiferromagnetic ordering. Between the charge/orbital ordering temperature ( T CO =220 K) and the antiferromagnetic transition temperature ( T N =170 K), unexpected hysteretic behaviour and field history dependence of the relaxation rates were observed. The field history dependence is observed by increased zero-field relaxation rates after switching the external field on and off again. These effects suggest field induced and residual magnetic correlations above T N which are presumably related to the formation of magneto-elastic polarons. No precession signal was observed for T T N , the only signature of the magnetic transition being the almost complete loss of asymmetry reflecting the wide field distribution at the muon site.