Temperature dependence of the samarium magnetic form factor in SmCo5

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Abstract
Results of polarized neutron experiments on SmCo5 at 4.2 K and 300 K are reported. To overcome the problem of the huge Sm absorption the measurements were made at short wavelengths, but on a single crystal containing natural samarium. The Co moments are close to those found in YCo5. The Sm form factor is very different at 4.2 K and 300 K, giving direct evidence for exchange and crystal field mixing of excited multiplets into the ground multiplet. The Sm moment is smaller at 300 K than at 4.2 K and its orbital character is less pronounced. The cross‐over is calculated to occur at 350 K above which temperature the spin contribution exceeds the orbital one. The compound is ferromagnetic below the cross‐over and ferrimagnetic above. The exchange and crystal field parameters deduced from our results are in agreement with previous determinations [1].