Abstract The addition of Cr to RE—TM-based magneto-optical layers is the most common way to gain chemical stability of such alloys. The disadvantage of Cr is its tendency to decreases the TM moments. This was observed by a shift of T comp to higher temperatures proportional to the amount of Cr. T C decreased significantly Cr content. The carrier-to-noise ratio of TbFeCoCr disks was 3–5 dB lower than for TbFeCo disks. The reduced TM moments led to a smaller Kerr rotation for wavelengths within the red and infrared region, resulting in a lower carrier level while the noise level did not change.