Magnetic Susceptibility of Colored Potassium Chloride from 1°K to 300°K

The magnetic susceptibility of potassium chloride crystals additively colored with an excess of potassium was measured from 1°K to 300°K. The excess magnetic susceptibility or the susceptibility of the color centers can be described by a temperature independent term which is predominant at room temperatures plus a temperature dependent term which obeys Curie's law and predominates in the liquid helium temperature range. It is suggested that the portion of the susceptibility following Curie's law is due to $F$-centers, and the temperature-independent contribution is due to color center complexes.