Neutron diffraction studies on several polycrystal and single crystal samples of Ho rich Tbsngbnd;Ho alloys are reported. Polycrystalline samples containing 90percnt;, 92percnt;, 94percnt;, 96percnt;, and 98percnt; Ho, as well as pure Ho, were studied at room temperature and at 8deg;K as a preliminary investigation for subsequent single crystal work. Three single crystal samples containing 93percnt;, 95percnt;, and 98percnt; Ho were studied in detail from room temperature to 4.2deg;K. Both the Curie and Neacute;el temperatures of the single crystal alloys were found to decrease almost linearly as the Ho concentration was increased. Both the 93percnt; and 95percnt; Ho alloys were found to have ordered phases similar to that of the 90percnt; Ho alloy, with the exception that fifth and seventh harmonics caused by the distortion of the simple helical arrangement were observed for 95percnt; Ho between 40deg;K and the Curie temperature at about 15deg;K. We find that the magnetic structure of the 98percnt; Ho alloy corresponds to a magnetic structure on the borderline between that of pure Ho and that of 90percnt; Ho. It shows all the characteristic features observed for pure Ho with the important exception that it does not transform to the conical spiral structure. Rather, the moments are still confined to the basal plane, most of them in the distorted helical arrangement bunched around the easybdirection, with some 4.4percnt; of them collapsed into ferromagnetic ordering along thebdirection.
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