First order reversal curves (FORC) analysis of individual magnetic nanostructures using micro-Hall magnetometry

Abstract

Alongside the development of artificially created magnetic nanostructures, micro-Hall magnetometry has proven to be a versatile tool to obtain high-resolution hysteresis loop data and access dynamical properties. Here we explore the application of First Order Reversal Curves (FORC)-a technique well-established in the field of paleomagnetism for studying grain-size and interaction effects in magnetic rocks-to individual and dipolar-coupled arrays of magnetic nanostructures using micro-Hall sensors. A proof-of-principle experiment performed on a macroscopic piece of a floppy disk as a reference sample well known in the literature demonstrates that the FORC diagrams obtained by magnetic stray field measurements using home-built magnetometers are in good agreement with magnetization data obtained by a commercial vibrating sample magnetometer. We discuss in detail the FORC diagrams and their interpretation of three different representative magnetic systems, prepared by the direct-write Focused Electron Beam Induced Deposition (FEBID) technique: (1) an isolated Co-nanoisland showing a simple square-shaped hysteresis loop, (2) a more complex CoFe-alloy nanoisland exhibiting a wasp-waist-type hysteresis, and (3) a cluster of interacting Co-nanoislands. Our findings reveal that the combination of FORC and micro-Hall magnetometry is a promising tool to investigate complex magnetization reversal processes within individual or small ensembles of nanomagnets grown by FEBID or other fabrication methods. The method provides sub-μm spatial resolution and bridges the gap of FORC analysis, commonly used for studying macroscopic samples and rather large arrays, to studies of small ensembles of interacting nanoparticles with the high moment sensitivity inherent to micro-Hall magnetometry.

Direct-write of free-form building blocks for artificial magnetic 3D lattices

“…Micro-Hall magnetometry, as sketched in Fig. 4(a) , is particularly well suited for measuring such stray fields of individual or small arrays of magnetic micro- and nanostructures 31 – 34 in a wide range of temperatures and external magnetic fields applied under various angles with respect to the magnetic structures. In Figs 4 and 5 we show stray field measurements of the 2 × 2 nano-cube and nano-tree arrays for selected inclination angles of the external magnetic field (see Fig.…”

First order reversal curve Hall analysis of zero-field skyrmions on Pt/Co/Ta multilayers

“…We seek to innovate, measuring the Hall effect in the construction of the FORC curves and subsequently producing the diagrams named FORC Hall. An advantage of using the FORC Hall diagrams is the greater sensitivity in the Hall effect measurements when compared to the magnetic measurement [22,23]. As it is also possible to measure Hall effect in lithography-made very small systems, the method is suitable for studying the nucleation of SKs in devices.…”

Electron-driven and thermal chemistry during water-assisted purification of platinum nanomaterials generated by electron beam induced deposition

“…Applications of this technology range from repair of masks for photolithography [ 2 ] and the fabrication of AFM tips [ 1 ] to novel photonic [ 3 – 4 ] or plasmonically active [ 5 ] devices and sensor concepts [ 6 ]. Also, nanoscale structures grown by FEBID may possess promising magnetic properties [ 7 – 8 ]. However, metallic nanostructures produced by FEBID are often contaminated by considerable amounts of carbon, preventing them from fulfilling their desired functionality [ 1 , 9 ].…”