* Corresponding author. Fax: #44-1865-272400. E-mail address: sjb@ermine.ox.ac.uk (S.J. Blundell). Physica B 289}290 (2000) 115}118 Muon studies of molecular magnetism S.J. Blundell*, A. Husmann, Th. Jesta K dt, F.L. Pratt, I.M. Marshall, B.W. Lovett, M. Kurmoo, T. Sugano, W. Hayes Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK RIKEN-RAL, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, UK IPCMS, 23 rue du Loess, BP 20/CR, 67037 Strasbourg Cedex, France Department of Chemistry, Meiji Gakuin University, Kamikurata, Totsuka-ku, Yokohama 244, Japan Abstract We present the results of SR experiments on a variety of molecular magnetic materials, either purely organic or combinations of transition metal ions and organic groups, which have been recently prepared. In a purely organic metamagnet, tanol suberate, we have observed a spin precession signal with a temperature dependence which has provided evidence of the two-dimensional nature of the antiferromagnetic ground state. In a family of dicyanamide-based molecular magnets with ordering temperatures of up to 21 K, and in a ferrimagnetic cobalt hydroxide, SR has been used to study the temperature dependence of the spin #uctuations.  2000 Elsevier Science B.V. All rights reserved. Keywords: Organic magnets; Molecular magnets; Tanol suberate 1. Introduction The preparation of organic and molecular mag- nets, via engineering of in"nite metal-organic poly- meric frameworks or the assembly of molecules with stable free radicals, has been the focus of much recent research [1}3]. Muon-spin rotation experi- ments can play a useful ro ( le in this "eld because of the unique local viewpoint which they bring [4,5]. However this technique can sometimes be compli- cated by multiple or unusual stopping sites. Never- theless in favourable circumstances, such as in certain nitronyl nitroxide organic magnets [4], easily interpretable spin-precession signals can be detected which provide a great deal of information. In this paper we report some recent experimental results concerning several organic and molecular magnets. SR experiments were carried out using the SR beamline at the ISIS facility, Rutherford Appleton Laboratory (UK) and also at the Paul Scherrer Institute (Switzerland). 2. Experimental results 2.1. Tanol suberate Tanol suberate is a biradical with formula (C  H  O  NO)  . The susceptibility follows a Curie}Weiss law with a positive Curie temper- ature ( #0.7 K). The spin density is found to be located on the NO group and almost equally shared between the oxygen and the nitrogen atoms 0921-4526/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 0 0 ) 0 0 2 7 3 - 8