Tunable magnetism and large inverse magnetocaloric effect in Shastry-Sutherland compounds Tb2Be2Si1-χGeχO7 (0 ≤ x ≤ 1)

The structure, magnetism and magnetocaloric effect (MCE) have been systematically investigated on the series of Tb2Be2Si1-chi Ge chi O7 (0 <= x <= 1) compounds, where the magnetic Tb3+ ions are located on the quasitwo-dimensional Shastry-Sutherland-Lattice (SSL). The X-ray diffraction measurements reveal that all compounds crystallize into the tetragonal structure with space group P (4) over bar2(1)m, the lattice parameters and nearest neighbor Tb-Tb distances increase monotonically with the variation of doping content x. All samples show the antiferromagnetic (AFM) ordered ground state and field (mu H-0) induced spin-flop (SP) transitions below Neel temperature (T-N). Moreover, the constructed field-temperature (mu H-0 - T) phase diagrams of Tb2Be2Si1-chi Ge chi O7 (0 = x = 1) reveal that the AFM phase shifts to the low temperature and low field sides with increased chi. Below T-N, we can observe a crossover behavior of MCE from the low-field (Delta mu H-0 < 2.58 T) inverse MCE (IMCE) to the CMCE at high fields (Delta mu 0H > 2.58 T). Among these serial compounds, Tb2Be2SiO7 exhibits the maximal IMCE with a value of 8.30 J kg(-1) K-1 under Delta mu H-0= 0.7 T and 2 K, comparable to the MCE (8.6 J kg(-1) K-1) of the benchmark material Tb3Ga5O12 at mu H-0 = 2 T. Additionally, it has a slightly better MCE performance than the materials RE3Ga5O12 (RE = Dy, Tb, Gd) under Delta mu H-0 = 2 T. The realization of large IMCE performance for Tb2Be2SiO7 provides an alternative route for magnetic refrigeration at low field and liquid Helium temperatures. (c) 2023 Elsevier B.V. All rights reserved.