Two-layer compounds in rare earth-{Fe, Co, Ni, Rh, Pd, Pt}-Te systems: crystal structure and magnetic properties

Highlights: • Partial {Gd, Ho}-Ni-Te and Gd-Co-Te isothermal sections were obtained at 1070K. • Twenty four new ternary compounds were found in Rare earth-{Fe,Co,Ni,Rh,Pd,Pt}-Te systems. • They are Y₅Ni₂Te₂-, Er₇Ni₂Te₂-, Fe₂P- and Sc₆PdTe₂-type compounds. • Y₅Ni₂Te₂-type {Gd,Tb,Dy,Ho}₅{Fe,Co,Ni}₂Te₂ exhibit ferromagnetic type of ordering. • Ho₅Ni₂Te₂ shows large MCE, while Tb₅{Fe, Co}₂Te₂ are giant LT permanent magnets. The partial isothermal sections of {Gd, Ho}-Ni-Te and Gd-Co-Te systems (~40–100at. % of rare earth) have been investigated at 1070K by X-ray and electron microprobe analysis. The Y₅Ni₂Te₂-type {Tb, Dy, Ho}₅Fe₂Te₂ and {Gd, Tb, Dy, Ho}₅{Co, Ni}₂Te₂ (space group Cmcm, No. 63, oC36), Er₇Ni₂Te₂-type Er₇Co₂Te₂, {Y, Dy, Ho}₇Ni₂Te₂, Ho₇{Rh, Pd}₂Te₂ and {Y, Gd}₇Pt₂Te₂ (space group Imm2, No. 44, oI22), Fe₂P-type Ho₆NiTe₂ (space group P-62m, No. 189, hP9) and Sc₆PdTe₂-type Ho₆{Rh, Pd}Te₂ and {Y, Gd}₆PtTe₂ (space group Pnma, No. 62, oP36) compounds have been established using powder X-ray diffraction studies. Magnetization measurements show that the Y₅Ni₂Te₂-type {Tb, Dy, Ho}₅Fe₂Te₂, {Gd, Tb, Dy}₅Co₂Te₂ and {Tb, Ho}₅Ni₂Te₂ compounds exhibit a high-temperature ferromagnetic ordering with low-temperature spin-reorientation transition for Tb-, Dy- and Ho-containing compounds. Below Curie temperature, Tb₅Fe₂Te₂, Tb₅Co₂Te₂ and Ho₅Ni₂Te₂ are soft ferromagnets, while they show hard magnetic properties below spin-reorientation transition. At 2K, Tb₅Co₂Te₂ and Tb₅Fe₂Te₂ exhibit a coercive field of 35kOe and ~30kOe and the residual magnetization of 17.2 μ_B and 22.9 μ_B per formula unit, leading to theoretical maximum energy product of ~620kJ/m³ and ~700kJ/m³, respectively. Ho₅Ni₂Te₂ reaches a maximum magnetic entropy change of −10.0J/kg⋅K and −9.4J/kg⋅K for a magnetic field change of 0–50kOeat 45K and 20K, respectively.