Antiferromagnetic resonance in the canted phase of La1-xSrxMnO3: Experimental evidence against electronic phase separation

Antiferromagnetic resonance (AFMR) experiments were performed in La1-xSrxMn O3 single crystals for Sr concentrations 0 less than or equal to x less tha n or equal to 0.1. A quasi-optical technique was employed in a frequency ra nge 2 cm(-1) < nu < 30 cm(-1) and for temperatures 3K < T < 300 K. Two AFMR modes, a quasi-ferromagnetic (F) and a quasi-antiferromagnetic (AF) mode, were observed for temperatures below T-N. The resonance frequency of the F- mode reveals a strong concentration dependence, while the AF-mode frequency only slightly decreases an increasing x. The observed concentration depend encies, as well as the excitation conditions for hath modes, can be explain ed using a simple two-sublattice model. These experiments provide direct. e vidence in favour of a canted antiferromagnetic (CA) structure for a < 0.1 and lo a temperatures and cannot be interpreted in terms of a phase separat ion of ferromagnetic droplets in an antiferromagnetic matrix.