Influence of a magnetic two-phase state on the magnetocaloric effect in the La1-xSrxMnO3 manganites

The magnetocaloric effect DeltaT(ex) and the magnetization in La(1-x)Sr(x)MnO(3)single crystals (x=0.1, 0.125, 0.175, 0.3) have been experimentally studied. The magnetic entropy and the magnetocaloric effect DeltaT(th) were computed from magnetization curves. All the samples exhibited a maximum in the DeltaT(th)(T) curve at T=T-max('). A step was observed on the DeltaT(ex)(T) curve in the region of T-max('), with the value of DeltaT(ex) on this step being substantially smaller than DeltaT(th). The step on the DeltaT(ex)(T) curve was followed by a maximum, which appeared at a temperature 20-40 K above T'(max). This anomalous behavior of DeltaT(ex) and DeltaT(th) is assigned to the coexistence of two magnetic (ferro- and antiferromagnetic) phases in the crystal. The calculated value of DeltaT(th) is determined primarily by the ferromagnetic part of the crystal and disregards the negative contribution from the antiferromagnetic part of the crystal to DeltaT(ex). (C) 2004 MAIK "Nauka/Interperiodica".