Polycrystalline Ho1-xTmxNi (0≤x≤0.8) compounds were successfully prepared by an arc-melting method, and the crystal structure, magnetic properties and magnetocaloric effect (MCE) were investigated in detail. X-ray diffraction (XRD) results indicate that Ho1-xTmxNi (0≤x≤0.8) compounds are pure phases with FeB-type orthorhombic structure (space group Pnma). Magnetic measurements show that HoNi alloy undergoes a spin reorientation (SR) transition and a ferromagnetic (FM) to paramagnetic (PM) transition at 13.5 K and 35.5 K, respectively. Rare earth atoms Tm with small spin were used to substitute Ho atoms in HoNi compound in order to adjust the magnetic phase transitions and to further optimize the magnetocaloric effect (MCE). With increasing Tm content from 0 to 0.8, the refrigerant temperature span decreases from 41.6 K to 17.3 K. When the content of Tm is 0.3, a platform-shaped isothermal magnetic entropy change (-ΔSM) curve is obtained and the value of -ΔSM is relatively stable over 35 K. Our findings are of great importance for HoTmNi compounds in practical applications.

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