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New data are presented for the low-field magnetisation and susceptibility of various Y9Co7 samples of difference metallurgical quality. These indicate the hysteresis at 4.2K is associated with imperfections, as in some PdCo alloys, and that not true long-range ferromagnetism sets in on cooling before superconductivity occurs. In the best sample the 4.2K Arrott plot is clearly not ferromagnetic; in the poorest samples the hysteresis persists to 15K and is accompanied by a weak feature in the AC susceptibility.
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Rastogi et al. (1985) studied this question.
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