Structural and magnetic properties of the R2Fe17−xGax compounds (R=Y, Ho, 0≤x≤6) have been investigated. All investigated Ho2Fe17−xGax compounds with x≳2.5 crystallize in the Th2Zn17‐type structure and the others in the Th2Ni17‐type structure. The substitution of Ga for Fe leads to an increase in lattice constants a, c, and unit‐cell volume, a decrease of the average Fe moment, and a maximum of the Curie temperature as a function of the Ga concentration at x=3, for both Y2Fe17−xGax and Ho2Fe17−xGax compounds. The high magnetic field leads to a spin phase transition from the ferromagnetic to the canted phase. The critical field Bc of the transition decreases with increasing Ga concentration. The exchange interaction constants JTT between Fe–Fe spins and JRT between R–T spins have been derived from a mean field analysis of Curie temperature. It has been found that JTT increases at first, going through a maximum at x=3, then decreases with increasing x, whereas JRT is almost independent of the Ga content, which is consistent with the result obtained from a mean field analysis of the high field magnetization curves of the Ho2Fe17−xGax.

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