Influence of a magnetic two-phase state on the magnetocaloric effect in the La1−x SrxMnO3 manganites

The magnetocaloric effect ΔTex and the magnetization in La1−xSrxMnO3 single crystals (x=0.1, 0.125, 0.175, 0.3) have been experimentally studied. The magnetic entropy and the magnetocaloric effect ΔTth were computed from magnetization curves. All the samples exhibited a maximum in the ΔTth(T) curve at T=Tmax′. A step was observed on the ΔTex(T) curve in the region of Tmax′, with the value of ΔTex on this step being substantially smaller than ΔTth. The step on the ΔTex(T) curve was followed by a maximum, which appeared at a temperature 20–40 K above Tmax′. This anomalous behavior of ΔTex and ΔTth is assigned to the coexistence of two magnetic (ferro-and antiferromagnetic) phases in the crystal. The calculated value of ΔTth is determined primarily by the ferromagnetic part of the crystal and disregards the negative contribution from the antiferromagnetic part of the crystal to ΔTex.