Magnetic properties of polycrystalline Sm0.1Ca 0.9-yBayMnO3 (y=0.02, 0.06) samples have been investigated in the temperature range of 2-320 K, magnetic fields of up to 90 kOe, and under hydrostatic pressures of up to 12 kbar. It was found that the volume fraction of ferromagnetic (FM) phase at 5 K is about 27% for Sm 0.1Ca0.88Ba0.02MnO3 and only ∼1% for Sm0.1Ca0.84Ba0.06MnO3. The compound Sm0.1Ca0.88Ba0.02MnO3 exhibits magnetic phase separation below TN ≈ TC ≈99 K, which is consistent with a model of FM clusters embedded in antiferromagnetic (AFM) G -type matrix. For this sample, magnetization and ac susceptibility exhibit a cluster glasslike behavior below TC, while the resistivity exhibits pronounced thermal hysteresis around TC, indicating upon a plausible first order magnetic phase transition. For Sm0.1Ca 0.84Ba0.06MnO3 two peaks observed in the temperature dependence of the ac susceptibility at low temperatures may be related to magnetic transitions, associated with the C - and G -AFM structures. Both, a significant hysteresis of magnetization observed at T<100 K and an increase in magnetoresistance at low temperatures are apparently an indicative of magnetic field induced structural transformation from monoclinic to orthorhombic phase. This transformation occurs concurrently with magnetic transition from C -type AFM to G -type AFM structure. It was found that an applied pressure enhances TC of Sm0.1Ca 0.88Ba0.02MnO3 with a pressure coefficient d TC/dP≈0.6 K/kbar. The spontaneous FM moment of Sm 0.1Ca0.88Ba0.02MnO3 decreases by 15% under pressure of about 12 kbar, while under the same pressure it only slightly increases for Sm0.1Ca0.84Ba0.06MnO 3. For both samples, the paramagnetic Curie temperature decreases under pressure indicating upon an increase in AFM interactions. Stronger suppression of the FM phase for the sample with y=0.06, in comparison with that one for 0.02 sample, is attributed to the effect of the chemical disorder, playing a more significant role than the effect related to the changes in 〈 rA 〉.
ASJC Scopus subject areas
- Physics and Astronomy (all)