Disclosed is a composite particle for use in a marking that is suitable for identification/authentication purposes. The particle comprises at least one superparamagnetic portion and at least one thermoluminescent portion coated with an thermoisolating portion. Optionally also a thermoconductive portion between the superparamagnetic and thermoluminscent portions.

The invention relates to a security feature for a security and/or value document which comprises a mixture of electrically conductive field displacement elements which are electrically insulated within the security or value document, and a zinc sulfide luminophore in the form of particles, which mixture is applied to a security and/or value document by means of a printing technology. The zinc sulfide luminophore has the general chemical formula ZnS: Cu.sub.x, M.sub.y, X.sub.z. Here, M represents one or more elements from a group comprising the chemical elements Co, In and Ni; X represents one or more elements from a group comprising the halides F, Cl, Br and I; 0<x0.002; 0<y0.00015; and 0z0.00050. The particles each have cubic phase fractions and hexagonal phase fractions, the zinc sulfide luminophore emitting a first luminescent radiation in the spectral range between 580 nm and 780 nm in the event of excitation by an electrical field, and the zinc sulfide luminophore emitting a second luminescent radiation in the visible spectral range in the event of thermal stimulation and preceding excitation by means of UV radiation. Furthermore, a security and/or value document having a security feature and a method for detection and/or verification of a security feature having a luminophore are provided.