Crystal structure and magnetic properties of the unique 154Sm0.6Sr0.4MnO3 Jahn-Teller system

Structural neutron diffraction investigations, as well as the data on the resistance, linear susceptibility, and second harmonic of magnetization, are presented for 154 Sm 0.6 Sr 0.4 MnO 3 manganite. Structural studies reveal the unique Jahn-Teller (JT) character of this compound, which is found to exhibit the Pbnm space group. Unusually large coherent JT distortions are found to develop below T JT 180 K and remain even in the metallic ferromagnetic phase below the Curie point T C 120 K. In the paramagnetic region, the resistance is consistent with polaron hopping. A field hysteresis of the second harmonic is observed above T C . This is evidence of the existence of macroscopic ferromagnetic regions in the paramagnetic matrix. In contrast, the temperature dependence of the linear susceptibility reveals a plateau at T> T C . These conflicting peculiarities of the magnetic properties can be explained by assuming the ferromagnetic behavior to be associated with antiferromagnetic regions with weak ferromagnetism.