An interchangeable scanning Hall probe/scanning SQUID microscope

Abstract

We have constructed a scanning probe microscope for magnetic imaging, which can function as a scanning Hall probe microscope (SHPM) and as a scanning SQUID microscope (SSM). The scanning scheme, applicable to SHPM and SSM, consists of a mechanical positioning (sub) micron-XY stage and a flexible direct contact to the sample without a feedback control system for the Z-axis. With the interchangeable capability of operating two distinct scanning modes, our microscope can incorporate the advantageous functionalities of the SHPM and SSM with large scan range up to millimeter, high spatial resolution (⩽4 μm), and high field sensitivity in a wide range of temperature (4.2 K-300 K) and magnetic field (10(-7) T-1 T). To demonstrate the capabilities of the system, we present magnetic images scanned with SHPM and SSM, including a RbFeB magnet and a nickel grid pattern at room temperature, surface magnetic domain structures of a La(2/3)Ca(1/3)MnO3 thin film at 77 K, and superconducting vortices in a striped niobium film at 4.2 K.

A scanning Hall probe microscope for high resolution, large area, variable height magnetic field imaging

“…SHPM is the tool of choice for quantifying the stray fields produced by micro-magnets, which have many applications in bio-medical studies [14][15][16] and MEMS [17]. The present SHPM system demonstrates the usefulness of a combination of concepts, tuning fork feedback based height control, monolithic electronics for regulation and Hall signal read out, scanning with stepper motors, compared to microscopes presented before [8][9][10][11][12][13]18]. Microstructured Hall probes with active area of size 1-5 µm have been fabricated for use in the microscope.…”

“…The noise depends on the active area of the probe and is larger for a smaller probe. In order to obtain understanding of the sensitivity limitations of our microscope let us compare the observed noise level to the Johnson-Nyquist thermal noise which limits the sensitivity of measurements [2,32,33]: , 20 µm [11]) and are significantly smaller than that in the probes used in the previous setup [18] (100 µm). As evident from the discussion above, the smaller distance in the present Hall probes has allowed achieving a much smaller probesample distance in the present setup ∼ 2 µm as compared to ∼ 25 µm in the previous setup).…”

“…Though SHPM involves longer image acquisition time than MOI unlike in a scanning probe system, in MOI the whole image is acquired at one time, and involves acquisition times of a few seconds at most) and offers worse spatial resolution compared to MFM, the unique compromise between spatial resolution and field sensitivity makes it a very useful tool for convenient non-destructive quantitative characterization over wide temperature and field ranges. Over the years, efforts have been made to improve the spatial resolution and scan range [8][9][10][11], temperature range [12], and magnetic field resolution [13] of SHPM.…”

Widefield quantum microscopy with nitrogen-vacancy centers in diamond: strengths, limitations, and prospects

“…Hall sensors and magnetic tunnel junctions can be fabricated down to a similar size of order 100 nm but with far lower field sensitivity than SQUIDs, of the order of 10 µT. [106][107][108][109][110] Hall probes have the advantage of operating at any temperature and magnetic field, but tend to be mechanically delicate and sensitive to destruction by electrostatic discharge. Magnetic tunnel junctions are designed to operate near room temperature and in low field only (below about 10 mT), and are magnetically invasive to the sample.…”

Hexapod Hall scanner for high-resolution large area magnetic imaging

“…[1][2][3][4] The non-invasive nature of the imaging process and the relative simplicity of the reconstruction procedure of the magnetic field distribution from a measured Hall voltage facilitate the use of the technique for a variety of applications. Some of these applications include the study of superconductors, [5][6][7] magnetic flux micro-sources, [8][9][10] magnetic domain structure in films, 11 and the magnetic phase transition in magneto-caloric materials. [12][13][14][15][16] The scan range of a Hall probe system depends on the type of scanning system employed.…”