At larger temperatures, the magnetization undergoes random thermal fluctuations (superparamagnetism) which present a limit for the use of nanomagnets for permanent information storage.
Canonical examples of nanomagnets are grains[1][2] of ferromagnetic metals (iron, cobalt, and nickel) and single-molecule magnets.
[3] The vast majority of nanomagnets feature transition metal (titanium, vanadium, chromium, manganese, iron, cobalt or nickel) or rare earth (Gadolinium, Europium, Erbium) magnetic atoms.
The ultimate limit in miniaturization of nanomagnets was achieved in 2016: individual Ho atoms present remanence when deposited on an atomically thin layer of MgO coating a silver film was reported by scientists from EPFL and ETH, in Switzerland.
Canonical single-molecule magnets are the so-called Mn12 and Fe8 systems, with 12 and 8 transition metal atoms each and both with spin 10 (S = 10) ground states.