A magnetoresistive random access memory die may include an MRAM cell, a reservoir defined by the MRAM die, and a chemical disposed in the reservoir. A marking device has a support mounted inside a housing, a light source unit holder swingably suspended by the support through a gimbal mechanism, and a light source unit mounted on the light source unit holder so as to diffuse a light flux only in a single direction to radiate a line of light. a C12-C16 alkyl ether sulfate;c.