A low-temperature ultrahigh vacuum scanning force microscope with a split-coil magnet

Abstract

We present the design of a scanning force microscope, which is optimized for magnetic force microscopy experiments. It can be operated at temperatures down to 5.2 K, in ultrahigh vacuum, and in magnetic fields of up to 5 T. Cooling is provided by a liquid helium bath cryostat, and the magnetic field is generated by a superconducting split-coil magnet. The design allows easy access from the side through a shutter system for fast in situ tip and sample exchange, while the microscope stays at temperatures below 25 K. The microscope itself features an all-fiber interferometric detection system, a 7.5×7.5 μm2 scan area at 5.2 K, and an xy table. The topographic resolution is demonstrated by imaging monoatomic steps on a nickel oxide surface, while magnetic contrast is shown on cobalt platinum multilayers and on a manganite perovskite film.

Chemical Resolution at Ionic Crystal Surfaces Using Dynamic Atomic Force Microscopy with Metallic Tips

“…[4]. All experiments were performed in an ultrahigh vacuum cryostat system with a homebuilt low temperature microscope [5] at about 8 K. The whole Si cantilever, including the tip, was coated in situ with nominally 4 nm of Cr, which adheres well to the oxide layer of standard Si tips, to produce a conducting path between tip apex and cantilever stage.…”

Construction of a 3He magnetic force microscope with a vector magnet

“…We employ a custom-built 3 He cryostat and a low-loss Dewar with a vector magnet from Janis, LLC [see Fig. 1(a)].…”

“…13 So far, several home-built low-temperature MFMs have been operated down to the 4 He temperature within a single axis magnet. 3,[14][15][16][17][18] On the other hand, MFM apparatus operating under high demanding conditions, such as sub-Kelvin temperatures and vector magnetic fields, are rare, 19,20 although they are useful for understanding unconventional (e.g., heavy fermion) superconductivity 21 and quantum/molecular magnetism at the nanoscale under extreme conditions. 22 At present, the demand for a sub-Kelvin MFM is high for investigating f -electron physics as a recent scanning tunneling microscopy study resolves the competition of f -and d-electrons in heavy fermion systems.…”

“…23,24 In addition, the use of a vector magnet allows further insight into anisotropy in superconductivity such as non-uniform pairing symmetry and magnetic penetration depth. 25 In this article, we report the construction of a 3 He MFM with a vector field of 2-2-9 T for the x-y-z direction and a base temperature of T = 300 mK. We calibrate the system's stray field by imaging Abrikosov vortices as a function of field and demonstrate its low temperature and vector field capabilities by resolving the coexistence of superconductivity and magnetism in a ferromagnetic superconductor at T = 500 mK, as well as by imaging the change of a single vortex shape depending on the direction of the tip magnetization.…”

“…Magnetic force microscopy (MFM), 1 a variant of AFM with a magnetized tip, plays an important role in studying the formation of magnetic domains in magnetic materials, [2][3][4] vortex dynamics in superconductors, [5][6][7][8][9][10][11][12] and exotic spin structures such as skyrmions. 13 So far, several home-built low-temperature MFMs have been operated down to the 4 He temperature within a single axis magnet.…”