Increased magnetocaloric response of La2/3Ca1/3MnO3/Gd nanocomposites in a large temperature range

Abstract

It has been known that a La2/3Ca1/3MnO3 (LMO) bulk sample has the maximum magnetic entropy change (|ΔSmax|) larger than |ΔSmax| of Gd – a conventional magnetocaloric (MC) material. However, such large change just takes place in a narrow range of temperature because of its first-order character. This influences the working temperature range (ΔT) and relative cooling power (RCP) of LMO. Previous works have revealed that the fabrication of LMO nanoparticles with the second-order character would improve the magnitude of ΔT and RCP, and reduce magnetic hysteresis losses. In this work, we suggest that the combination of LMO nanoparticles (NPs) with Gd powder as nanocomposites (NCPs), termed (100-x)LMO + xGd with x = 50 and 75 wt%, further enhances ΔT from 60 to ∼94 K (in the range T = 220–314 K) for applied fields H = 5–20 kOe. These values are larger than those of initial materials Gd and LMO NPs (ΔT ≈ 40 K), reported composites (ΔT < 50 K), and even the composites fabricated from a LMO bulk and Gd powder (ΔT < 60 K) in the same fields. Additionally, all NCPs exhibit the second-order character, and RCP of optimal NCPs is nearly comparable to that of Gd. These features demonstrate application potentials of NCPs for conventional refrigerators operating in a large temperature range.