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Hyperfine Splitting and Room-Temperature Ferromagnetism of Ni at Multimegabar Pressure

I. Sergueev, L. Dubrovinsky, M. Ekholm, O. Yu. Vekilova, A. I. Chumakov, M. Zajac, V. Potapkin, I. Kantor, S. Bornemann, H. Ebert, S. I. Simak, I. A. Abrikosov, R . Rüffer

PRL 111, 157601 (2013)

Magnetic and elastic properties of Ni metal have been studied up to 260 GPa by nuclear forward scattering of synchrotron radiation with the 67.4 keV Mo ̈ssbauer transition of 61 Ni . The observed magnetic hyperfine splitting confirms the ferromagnetic state of Ni up to 260 GPa, the highest pressure where magnetism in any material has been observed so far. Ab initio calculations reveal that the pressure evolution of the hyperfine field, which features a maximum in the range of 100 to 225 GPa, is a relativistic effect. The Debye energy obtained from the Lamb-Mo ̈ ssbauer factor increases from 33 meV at ambient pressure to 60 meV at 100 GPa. The change of this energy over volume compression is well described by a Gru ̈ neisen parameter of 2.09.

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Last updated: 10/14/13