A novel variable temperature scanning nano-Hall probe microscope system for large area magnetic imaging incorporating piezoelectric actuators maintained at room temperature

Abstract

A unique variable temperature scanning Hall probe system (VT-SHPM) has been developed for large area, nanometre scale lateral resolution imaging of ferromagnetic domains, in which piezoelectric actuators are maintained at ambient temperature and only the semiconducting micro-Hall probe and sample are cooled. Its design overcomes the limitations of conventional cryogenic SHPM systems, where the piezoelectric actuators are cooled thus reducing the maximum scan area to about 10 µm × 10 µm due to a reduction of the piezoelectric constant at cryogenic temperatures. The VT-SHPM operates between 300 and 77 K and consists of a liquid nitrogen glass Dewar housing the sample and the semiconducting micro-Hall probe (active area = 900 nm × 900 nm; magnetic sensitivity at 300 K 6 mG Hz−1/2) used to detect surface magnetic fields. The VT-SHPM was used to image perpendicularly magnetized domains at the surfaces of 5.5 µm thick single crystal bismuth substituted garnet thin films between 300 and 77 K. Areas of about 120 µm × 130 µm were readily imaged by synchronizing the action of x–y piezoelectric actuators and corresponding stepper motors to move and scan the sample at a constant height of 0.25 µm over the surface of the micro-Hall probe. The average width of magnetic domains in the garnet thin films was found to increase as the measurement temperature decreased.

Submicrometer Hall devices fabricated by focused electron-beam-induced deposition

“…[4][5][6][7][8][9] The ordinary Hall effect is due to the Lorentz force acting on charge carriers in metals, semi-metals, and semiconductors.…”

“…[1][2][3][4] Hall effect devices are emerging as one of the most suitable solutions. [4][5][6][7][8][9] The ordinary Hall effect is due to the Lorentz force acting on charge carriers in metals, semi-metals, and semiconductors. 5 Magnetic materials show additional "Hall phenomena" which are, generally speaking, generated by spin-orbit interactions: the so-called extraordinary [10][11][12][13][14][15][16] and planar Hall effects.…”

Magnetoresistive Sensors for Surface Scanning

“…But many SHPM systems are developed to image superconducting materials and must work at cryogenic temperatures [42]. Several authors worked to overcome the small scan range of cooled piezoelectric crystals, either by using stepping motors effectively increasing the range to the centimeter scale [43][44][45] or by keeping piezoelectric scanner at room temperature while the sample is cooled [41]. Also, in order to reduce the infrastructure needed to operate the systems, others integrated a Stirling cycle refrigeration system allowing the operation at 35 K without the need for cryogenic fluids [46].…”

Variable temperature scanning Hall probe microscopy of ferromagnetic garnet thin films

“…Recently, we reported on the use of scanning Hall probe microscope (SHPM) as a highly sensitive, noninvasive and quantitative means of sensing localized stray fields at the surfaces of magnetic recording media, garnet thin films and permanent magnet under an external magnetic field [2]. Further, we have described the features of a variable temperature SHPM (VT-SHPM) system for imaging large areas even at cryogenic temperatures [3].The design of the VT-SHPM overcomes the limitations of conventional cryogenic SHPM systems, where cooling of piezoelectric actuators limits the maximum scan area to about 10 mm  10 mm due to reduction of piezoelectric constants at cryogenic temperatures. Here, we describe magnetic imaging of ferromagnetic domains at the surface of bismuth substituted iron garnet thin films (BiTbHo) 3-Fe 5 O 12 with perpendicular anisotropy between 77 K and 300 K and the temperature dependence of domain widths and magnetization.…”

“…Recently, we reported on the use of scanning Hall probe microscope (SHPM) as a highly sensitive, noninvasive and quantitative means of sensing localized stray fields at the surfaces of magnetic recording media, garnet thin films and permanent magnet under an external magnetic field [2]. Further, we have described the features of a variable temperature SHPM (VT-SHPM) system for imaging large areas even at cryogenic temperatures [3].…”