tailieunhanh - Báo cáo " Room-temperature large magnetocaloric effect in perovskites (La1-xNdx)0.7Sr0.3MnO3 "

Study of the effect of Nd substitution for La on magnetocaloric effect (MCE) of polycrystalline perovskites (La1-xNdx) (x = , , , , , ) is presented. Large MCE is observed in all samples. The presence of Nd affects to both maximum magnetic entropy change, |∆Sm|max, and Curie temperature, TC. |∆Sm|max slightly reduces with low content and increases with high content of Nd and gets maximum value of J/ for x = . TC of the samples determined from the | VNU Journal of Science Mathematics - Physics 24 2008 30-35 Room-temperature large magnetocaloric effect in perovskites La1-xNdx Nguyen Hoang Luong1 Nguyen Thi Mai Phuong1 2 Phung Thu Hien1 Hoang Nam Nhat1 Luc Huy Hoang2 Nguyen Chau1 Nguyen Hoang Hai1 1 Center for Materials Science College of Science Vietnam National University Hanoi 334 Nguyen Trai Hanoi Vietnam 2 Hanoi University of Education 136 Xuan Thuy Hanoi Vietnam Received 5 March 2008 Abstract. Study of the effect of Nd substitution for La on magnetocaloric effect MCE of polycrystalline perovskites La1-xNdx x is presented. Large MCE is observed in all samples. The presence of Nd affects to both maximum magnetic entropy change ASm max and Curie temperature TC. ASm max slightly reduces with low content and increases with high content of Nd and gets maximum value of J for x . TC of the samples determined from the thermomagnetic curves somewhat increases from 346 K for x to 350 K for x then decreases to 235 K for x . The sample with x exhibiting the largest value of 74 J kg for the relative cooling power among the studied samples has TC 325 K . higher than room temperature. Our studied samples are promising materials for magnetic refrigerants in the room-temperature region. Keywords Magnetocaloric effect perovskites manganites. 1. Introduction The magnetocaloric effect MCE is detected as the heating or the cooling of magnetic materials due to a varying magnetic field. Magnetic refrigeration provides an alternative method for cooling 1 2 . The material used to provide the MCE is called a magnetic refrigerant. The MCE has been used for many years to obtain low temperatures of the order of milikelvins through adiabatic demagnetization of paramagnetic salts 3 . At present the magnetic refrigeration around room temperature is of particular interest because of potential impact on energy savings as well as environme ntal concerns the .