Investigating the magnetic and magnetocaloric behaviors of LiSm(PO 3 ) 4 .

We report a detailed study on the magnetic behaviors and magnetocaloric (MC) effect of a single crystal of lithium samarium tetraphosphate, LiSm(PO 3 ) 4 . The analyses of temperature-dependent magnetization data have revealed magnetic ordering established with decreasing temperature below T p , where T p is the minimum of a d M /d T vs. T curve and varies as a linear function of the applied field H . The Curie temperature has been extrapolated from T p ( H ) data, as H → 0, to be about 0.51 K. The establishment of magnetic-ordering causes a substantial change in the heat capacity C p . Above T p , the crystal exhibits paramagnetic behavior. Using the Curie-Weiss (CW) law and Arrott plots, we have found the crystal to have a CW temperature θ CW ≈ -36 K, and short-range magnetic order associated with a coexistence of antiferromagnetic and ferromagnetic interactions ascribed to the couplings of magnetic dipoles and octupoles at the Γ 7 and Γ 8 states. An assessment of the MC effect has shown increases in value of the absolute magnetic-entropy change (|Δ S m |) and adiabatic-temperature change (Δ T ad ) when lowering the temperature to 2 K, and increasing the magnetic-field H magnitude. Around 2 K, the maximum value of |Δ S m | is about 3.6 J kg -1 K -1 for the field H = 50 kOe, and Δ T ad is about 5.8 K for H = 20 kOe, with the relative cooling power (RCP) of ∼82.5 J kg -1 . In spite of a low MC effect in comparison to Li(Gd,Tb,Ho)(PO 3 ) 4 , the absence of magnetic hysteresis reflects that LiSm(PO 3 ) 4 is also a candidate for low-temperature MC applications below 25 K.