Magnetism and magnetocaloric effect in the RE2CuSi3 (RE = Dy and Ho) compounds
Introduction
Ternary rare-earth based compounds RE2TX3 (RE = rare earth element or U, T = transition metal element, and X = p block element) became a subject of intensive investigations in the past years [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]. Many members of 2:1:3 type compounds are crystallized in the hexagonal AlB2- or CaIn2- type crystal structures (space group P6/mmm, or its derivatives), consisting of rare earth RE magnetic layers and alternating with statistically mixed nonmagnetic ion M-X layers along the c-axis [7]. The RE2TX3 compounds exhibit some unusual physical properties which are related to distinctive electronic structures, crystal structures, microstructure, as well as external environment. These include large magnetoresistance (MR) [1], [3], magnetic order at low temperature [2], collinear antiferromagentism (AFM) [8], canonical spin glass behavior (SG) [9], Kondo effect [6], heavy fermion behavior [10], giant magnetocaloric effect (MCE) [11], and so on. Among of them, MCE has attractive much attention since it is the origin of the magnetic refrigeration, and which is known as consequent changes in the entropy and temperature for all the magnetic materials to a changing magnetic field. In recent years, rare-earth based compounds have been devoted intense research effort, and large magnetic entropy change (ΔSM) without thermal and magnetic hysteresis loss have been found in a lot of compounds, thereby becoming suitable candidates for application in magnetic refrigeration [12], [13], [14], [15], [16], [17], [18], [19].
RE2CuSi3 in RE2TX3 system has been a focal point of research because of some interesting physical properties. It has been reported that the Ce2CuSi3 shows cluster glass below its spin freezing temperature [10], while the Eu2CuSi3 shows ferromagnetic behavior below its Curie temperature [20]. The Pr2CuSi3 and Nd2CuSi3 exhibit unusual ferromagnetic characteristics with a SG-like effect [5], [7], which is very different from typical SG materials of the 2:1:3 system. In spite of the above-mentioned studies, to our knowledge, the magnetocaloric properties of RE2CuSi3 compounds are still lacking. Moreover, the previous results illustrated that RECuSi compounds possess giant/large MCE and can be as candidates of the magnetic refrigerator [21], [22], [23], which hints a desired MCE may be observed in RE2CuSi3 compounds. With the aim of further understanding the physical properties of RE2CuSi3 and exporting for new magnetic materials, we carry out a study on the magnetic and magnetocaloric properties of Dy2CuSi3 and Ho2CuSi3 compounds in the present work. A large field-induced reversible MCE with considerable relative cooling power was observed in both compounds.
Section snippets
Experimental
Polycrystalline Dy2CuSi3 and Ho2CuSi3 samples with a mass of about 5 g were synthesized by arc melting high purities start elements Dy, Ho, Cu and Si (3% excess Dy and Ho were included in the starting materials) under a high purified argon atmosphere. To ensure homogeneity each of prepared buttons was turned over and re-melted more than four times. The samples were wrapped into tantalum foil, sealed in an evacuated quartz glass tube, annealed at 1173 K for 7 days, and a subsequent quenched into
Results and discussion
Fig. 1 and Fig. 2 present the temperature dependence of the magnetization M (left scale) together with the reciprocal susceptibility 1/χ (right scale) under an applied magnetic field of 10 kOe for Dy2CuSi3 and Ho2CuSi3 compounds, respectively. The temperature dependence of the zero field cooled (ZFC) and field cooled (FC) magnetization M protocols under a low magnetic field H = 2 kOe for Dy2CuSi3 and Ho2CuSi3 also were given in the insets of Fig. 1, Fig. 2 (left scale), respectively. Both
Conclusions
In summary, we have investigated the magnetism, magnetocaloric properties and magnetic phase transition of two single phased Dy2CuSi3 and Ho2CuSi3 ternary compounds. A large reversible MCE is observed in both compounds accompanied by a second order magnetic phase transition from PM to FM state at their own Curie temperature of TC ∼9.6 and 6.3 K, respectively. Moreover, the second order phase transition in both compounds is further confirmed by the rescaling magnetic entropy change curves that
Acknowledgements
The present work was partially supported by the National Natural Science Foundation of China (No. 51501036).
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