A low-temperature scanning tunneling microscope capable of microscopy and spectroscopy in a Bitter magnet at up to 34 T

Abstract

We present the design and performance of a cryogenic scanning tunneling microscope (STM) which operates inside a water-cooled Bitter magnet, which can attain a magnetic field of up to 38 T. Due to the high vibration environment generated by the magnet cooling water, a uniquely designed STM and a vibration damping system are required. The STM scan head is designed to be as compact and rigid as possible, to minimize the effect of vibrational noise as well as fit the size constraints of the Bitter magnet. The STM uses a differential screw mechanism for coarse tip-sample approach, and operates in helium exchange gas at cryogenic temperatures. The reliability and performance of the STM are demonstrated through topographic imaging and scanning tunneling spectroscopy on highly oriented pyrolytic graphite at T = 4.2 K and in magnetic fields up to 34 T.

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.…”

Ultracompact Binary Permanent Rare-Earth Magnet with 1.25-T Center Field and Fast-Decaying Stray Field

“…Afterwards, it is immediately introduced into the STM space and evacuated to a pressure better than 10 −7 mbar. The STM measurements are done in a 3 He cryostat [22] at a base temperature of 400 mK in a cryogenic vacuum of < 10 −8 mbar.…”

“…Generating strong magnetic fields (1 T and above) typically involves cumbersome and heavy electrical magnets or cryogenic superconducting coils [1][2][3][4][5]. Such equipment is not compatible with all experiments and does not allow magnetic fields to be easily retrofitted to existing experiments.…”

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

“…The z resolution at high field is thus comparable to a commercial AFM. As with the high-field STM 14 , the x-y resolution is likely limited by the vibrational modes of the 40 mm long scan tube, but it is sufficient for scan modes such as MFM. Figure 4…”