Improving the sensitivity of DC magneto-optical Kerr effect measurement to 10−7rad/Hz

Abstract

A high-sensitivity DC magneto-optical Kerr effect (MOKE) apparatus is described in this Letter. Via detailed analysis on several dominating noise sources, we have proposed solutions that significantly lower the MOKE noise, and a sensitivity of 1.5 × 10 −7 rad= Hz p is achieved with long-term stability. The sensitivity of the apparatus is tested by measuring a wedgeshaped Ni thin film on SiO 2 with Ni thickness varying from 0 to 3 nm. A noise floor of 1.5 × 10 −8 rad is demonstrated. The possibility of further improving sensitivity to 10 −9 rad via applying AC modulation is also discussed.

Magneto-optical Kerr Effect in Ferroelectric Antiferromagnetic Two-Dimensional Heterostructures

“…Because scriptI is equivalent to scriptM z scriptC 2 , where scriptM z is the mirror reflection symmetry (mirror perpendicular to the z direction) and scriptC 2 is the in-plane inversion symmetry, the activation of MOKE can be achieved by breaking either scriptM z or scriptC 2 , as confirmed by some theoretical and experimental reports. ,, In general, MOKE is not active in antiferromagnetic systems, where the net magnetization is zero and the scriptT scriptI symmetry is usually preserved. However, several first-principles and experimental studies have predicted or verified a non-negligible MOKE in some antiferromagnets, where the scriptT scriptI symmetry is broken by either the spatial asymmetry or chirality of the crystal or spin structure even though the net magnetization is zero. ,,− In addition to its fundamental interest, the presence of MOKE in an antiferromagnet introduces additional perspectives, because, on the one hand, it challenges the traditional microscopic origin of the Kerr effect, while, on the other hand, it can be exploited in antiferromagnetic spintronics as a result of the insensitivity to external magnetic fields and ultrafast terahertz (THz) spin dynamics. − …”

“…7,8,[10][11][12][13][14][15][16] In addition to its fundamental interest, the presence of MOKE in an antiferromagnet introduces additional perspectives, since, on the one hand, it challenges the traditional microscopic origin of the Kerr effect, on the other hand, it can be exploited in antiferromagnetic spintronics due to the insensitivity to external magnetic fields and ultrafast THz spin dynamics. [17][18][19][20] Recently, two-dimensional (2D) materials have been heavily studied since they show interesting physical properties different from bulk systems and can be exploited for miniaturized nanoelectronic components. [21][22][23] In particular, monolayer CrI 3 , one of the first experimentally synthesized 2D magnets, has opened a new era in the study of 2D ferromagnetic materials.…”