An ultra-compact low temperature scanning probe microscope for magnetic fields above 30 T

Abstract

We present the design of a highly compact High Field Scanning Probe Microscope (HF-SPM) for operation at cryogenic temperatures in an extremely high magnetic field, provided by a water-cooled Bitter magnet able to reach 38 T. The HF-SPM is 14 mm in diameter: an Attocube nano-positioner controls the coarse approach of a piezo resistive AFM cantilever to a scanned sample. The Bitter magnet constitutes an extreme environment for SPM due to the high level of vibrational noise; the Bitter magnet noise at frequencies up to 300 kHz is characterized and noise mitigation methods are described. The performance of the HF-SPM is demonstrated by topographic imaging and noise measurements at up to 30 T. Additionally, the use of the SPM as a three-dimensional dilatometer for magnetostriction measurements is demonstrated via measurements on a magnetically frustrated spinel sample.

A new view on the origin of zero-bias anomalies of Co atoms atop noble metal surfaces

“…The spinexcitation gap opens while the dip moves to larger energies. Large magnetic field are possible in some STS setups (14 T 45 or even 38 T 46,47 ). d Proximity effects can be used via neighboring adatoms and by depositing thin films of noble metals on a ferromagnetic substrate, where the magnetic exchange interaction felt by the adatom acts as an effective magnetic field.…”

“…We note that applying a magnetic field in the direction perpendicular to the magnetic moment, would affect the excitation gap in a nontrivial way 32 . A field of 14 Tesla is available in some STS setups 45 and can even reach 38 Tesla 46,47 . Larger fields can be accessed effectively via magnetic-exchange-mediated proximity effect by either (i) bringing another magnetic atom to the vicinity of the probed adatom or (ii) depositing the probed adatom on a magnetic surface with a non-magnetic spacer in-between (see Fig.…”

A new view on the origin of zero-bias anomalies of Co atoms atop noble metal surfaces

“…. A field of 14 Tesla is available in some STS setups 42 and can even reach 38 Tesla 43,44 . Larger fields can be accessed effectively via magnetic-exchange- surfaces.…”

Magnetoelectric coupling in a frustrated spinel studied using high-field scanning probe microscopy

“…We measure the field-induced electric polarization both via a standard polarization current (pyrocurrent) technique, and by measuring the contact potential difference (CPD) between the sample surface and the tip of a scanning probe microscope, in a static magnetic field up to 30 T generated by a Bitter magnet. In order to perform these a) Electronic mail: ben.e.bryant@gmail.com; Current address: Oxford Instruments NanoScience, OX13 5QX, United Kingdom measurements, we employed a high-field scanning probe microscope (HF-SPM) 13 . The SPM technique has the advantage of being able to measure the surface polarization within an area much smaller than the size of the tetragonal structural domains, circumventing the problems these domains present for traditional polarization measurements.…”

“…By applying a bias voltage to the sample via a silver paste connection, we could measure the voltage which is induced at the surface of the sample, due to the bulk polarization. For this purpose, an SPM able to work in high magnetic field was employed 13 . We operated the HF-SPM at 4.4 K, in He-exchange gas at a pressure of around 10 −2 mbar.…”