Amorphous and crystallized (Gd4Co3)100−xBx alloys for magnetic refrigerants working in the vicinity of 200 K

► The Ho4Co3-type hexagonal phase was obtained for fully crystallized ribbons. ► B substitution leads to almost no change in the MCE behavior of crystalline alloys. ► The (−ΔSM) for amorphous alloys increases with increasing B content. ► (Gd4Co3)100−xBx amorphous alloys are good candidates working near 200 K.