Effect of ball milling and Ho doping on structural, magnetic and magnetocaloric properties of Yb2O3

Magnetic refrigeration in the liquid-helium temperature region plays a significant role in many technological fields. In this work, the crystal structure, magnetic properties, and magnetocaloric effect (MCE) of commercial Yb 2 O 3 and a series of (Yb 1-x Ho x ) 2 O 3 (x = 0, 0.1, 0.2) compounds prepared by a feasible high-energy ball milling method were systematically investigated. The crystallography results demonstrate that these Yb 2 O 3 -based compounds have a cubic bixbyite structure with space group Ia 3 ¯ , and the lattice constant increases with the increase of Ho 3+ ions content. Commercial Yb 2 O 3 shows antiferromagnetic (AFM) ordering at 2.35 K, and ball-milled (Yb 1-x Ho x ) 2 O 3 (x = 0, 0.1, 0.2) compounds have lower AFM ordering temperatures of RE 3+ moments of 2.30 K, 2.15 K and below 2 K for x = 0, x = 0.1 and x = 0.2 samples, respectively. Thermomagnetic behavior under high magnetic fields exhibited the existence of ferromagnetic (FM) correlation in these compounds, and a high magnetic field could induce an AFM to FM transition. The magnetization of Yb 2 O 3 increases with the increase of Ho 3+ ions content due to the increase of the effective magnetic moments. The maximum magnetic-entropy change Δ S M and relative cooling power RCP of (Yb 0.8 Ho 0.2 ) 2 O 3 are 11.1J/kg·K and 123.2 J/kg, respectively under 5 T, which are 19.4 % and 67.6 % larger than those of commercial Yb 2 O 3 . The (Yb 1-x Ho x ) 2 O 3 (x = 0, 0.1, 0.2) compounds have a large MCE under moderate magnetic field changes and there is no thermal and magnetic hysteresis, which is beneficial for application as a promising refrigerant near the liquid-helium temperature range.