Rights:
© 1990 American Physical Society (APS). This is the accepted version of the following article: Hakonen, Pertti J. & Yin, S. & Lounasmaa, O. V. 1990. Nuclear magnetism in silver at positive and negative absolute temperatures in the low nanokelvin range. Physical Review Letters. Volume 64, Issue 22. 2707-2710. ISSN 0031-9007 (printed). DOI: 10.1103/physrevlett.64.2707, which has been published in final form at http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.64.2707.