Magnetic behavior ofEu2CuSi3:Large negative magnetoresistance above the Curie temperature

Abstract

We report here the results of magnetic susceptibility, electrical-resistivity, magnetoresistance (MR), heat-capacity and 151 Eu Mössbauer effect measurements on the compound, Eu2CuSi3, crystallizing in an AlB2-derived hexagonal structure. The results establish that Eu ions are divalent, undergoing long-range ferromagnetic-ordering below (TC =) 37 K. An interesting observation is that the sign of MR is negative even at temperatures close to 3TC , with increasing magnitude with decreasing temperature exhibiting a peak at TC . This observation, being made for a Cu containing magnetic rare-earth compound for the first time, is of relevance to the field of collosal magnetoresistance.

Structural and magnetic properties of Nd2NiGe3

“…In the low temperature range, there is a sudden drop in resistivity near 3 K and it sharply decreases with further decrease in temperature. This could arise due to onset of ferromagnetic ordering as also observed in another AlB 2 type compound, Eu 2 CuSi 3 [59,60]. At temperatures below 10 K, the q(T) data can be fitted to the power law function, q = q 0 + AT n , where q 0 is the residual resistivity expressed in units of lX cm and A and n are the fitting parameters [61].…”

Single crystal growth of Eu2CuSi3 intermetallic compound by the floating-zone method

“…The inset exhibits the interface of Eu 2 CuSi 3 and EuCu 2 Si 2 , as well as intradendritic Eu 2 SiO 4 oxide. The data in the zero-field-cooled and field-cooled state for polycrystals at B ¼0.01 T are also presented for comparison (solid symbols) [2], showing ferromagnetic order at 37 K and another possible magnetic transition at around 5 K. The most pronounced feature for the single crystal is the strong increase in the magnetic susceptibility w(T) at low temperatures for both orientations, which implies the evolution of a spontaneous magnetic moment, corresponding to ferromagnetic ordering at T C ¼ 34 K. However, there is a great anisotropy of the magnetic properties between a steep increase in magnetic susceptibility along the c-axis, which represents the easy magnetic axis, and the moderate increase along the a-axis in the basis plane perpendicular to the c-axis. Beginning at TE28 K there is a second magnetic order transition connected with a rise in magnetic susceptibility for both orientations.…”

“…5. The data have been normalized to the resistance at T¼295 K. The data at B ¼0 and 3 T for polycrystals from literature [2] are also presented. The temperature dependence of the normalized electrical resistivity r(T)/ r(295 K) basically reflects the metallic behavior.…”

“…Studies on Eu compounds are scarce due to the difficulties in controlling the Eu stoichiometry during sample preparation. Both Eu 2 PdSi 3 and Eu 2 CuSi 3 , crystallizing in an AlB 2 -type hexagonal structure [13,14], show complex magnetic behavior of ferromagnetic type, but Eu 2 CuSi 3 exhibits a large negative magnetoresistance above the Curie temperature [2]. The Mössbauer spectrum shows that europium in this compound is in a stable divalent state [14].…”

“…Most compounds of the class R 2 TSi 3 (T¼ Pd, Rh, Ni, and Cu) exhibit a hexagonal AlB 2 -type crystallographic structure and interesting physical properties [1][2][3][4][5][6][7][8][9][10][11][12]. Among the lanthanides europium is special because it has a half-filled 4f shell.…”