Magnetometry means gaining information about magnetic properties. SQUID-mag
netometry, neutron depolarisation and Mossbauer effect spectrometry are exa
mples of very useful experimental methods for investigating magnetic system
s consisting of small particles. Small in magnetic sense means that the par
ticles represent single domains. Often their dimensions are in the order of
nanometers. This kind of particles can be found in many magnetic systems l
ike super-paramagnets, cluster re-entrant spin glasses or nanostructured so
ft magnetic alloys. In this paper, examples of experiments performed with t
hese techniques will be discussed. Magnetisation measurements performed on
nano Ni-particles fixed in space, neutron depolarisation measurements on re
-entrant spin glasses (i.e. disordered Fe-Ni-Mn alloys) and transmission Mo
ssbauer effect measurements on nanostructured soft magnetic materials (Fe-N
b-Cu-Si-B) with the use of high frequency magnetic fields will be considere
d. The physical understanding of all these processes is strongly supported
by the basic assumptions and properties of Stoner-Wohlfarth particles. (C)
2001 Elsevier Science BY All rights reserved.