Use of radiofrequency wave absorbing markets for the authentication of security documents

A method for preparing or marking a security document or article, said method comprising incorporating in said security document or article a composition comprising a combination of at least two types of particles of inorganic oxide materials,

• where each of the at least two types of particles has a different size or a different morphology, and
• where the inorganic oxide materials have at least one transition metal or one lanthanide element, and radiofrequency wave absorption properties.

A security article, document or element comprising a composition comprising a combination of at least two types of particles of inorganic oxide materials,

• where each of the at least two types of particles has a different size or different morphology, and
• where the inorganic oxide materials have at least one transition metal or one lanthanide element, and radiofrequency wave absorption properties.

A chemical composition for preparing or marking a security document or article, comprising a combination of at least two types of particles of inorganic oxide materials,

• where each of the at least two types of particles has a different size or different morphology, and
• where the inorganic oxide materials have at least one lanthanide element, and radiofrequency wave absorption properties.