Complex switching behavior of magnetostatically coupled single-domain nanomagnets probed by micro-Hall magnetometry

Abstract

We report here the results of two-dimensional electron gas based micro-Hall magnetometry measurements and micromagnetic simulations of dipolar coupled nanomagnets of Ni80Fe20 arranged in a double square ring-like geometry. We observe that although magnetic force microscopy images exhibit single domain like magnetic states for the nanostructures, their reversal processes may undergo complex behavior. The details of such reversal behavior are observed as specific features in micro-Hall magnetometry data, which are comparable with the micromagnetic simulation data.

Tailoring magnetization reversal of a single-domain bar nanomagnet via its end geometry

“…The material parameters of permalloy (Ni80Fe20) were used in our investigation because it is a soft magnetic alloy with very large permeability, and more importantly, it is one of the most widely used materials in related research [1][2][3][4][5][6][7][8][9][10][11][12][15][16][17][18][19][20] . The material parameters were set as standard values widely used for permalloy [25][26][27][28][29][30] : the saturation magnetization (MS) is 8.6×10 5 A/m and the damping constant is 0.5 in order to quickly minimize the energy. The exchange stiffness (A) and the crystalline anisotropy constant (K) were 13×10 -12 J/m and 0 J/m 3 .…”

“…S3), can also modulate the magnetization reversal. The ability to control the magnetization reversal of a single-domain bar magnet could lead to complex magnetization reversal behavior in coupled nanomagnet systems 29 . Fabricating arrays of nanomagnets with tailored magnetization reversal switching fields would enable modulation of phase transition temperatures and/or magnetic fields in artificial spin ices, which could greatly affect the access to ground state configurations as well as realizing novel excited low energy states.…”

Magnetic characterization techniques and micromagnetic simulations of magnetic nanostructures: from zero to three dimensions

“…Micro-Hall magnetometry involves magnetic field measurement devices based on miniature Hall sensors, including micro-Hall magnetic sensing techniques based on 2D electronic systems (2D electron gases) in semiconductor heterostructures and epitaxial graphene magnetometry with room-temperature Hall coefficients, where graphene Hall sensors offer significantly improved performance and durability compared to conventional semiconductor devices. 70,71 Fig. 2g depicts the measured image of a single Fe nanoparticle's micro-Hall magnetometry based on a 2D electronic system (gradiometry), where a net hysteresis loop with an approximately rectangular shape is obtained by subtracting the nonlinear background from the raw Hall signal.…”

“…11c). It is evident from the preceding discussion that micro-Hall magnetometry can be used to measure individual low-dimensional MNs (such as nanoparticles, 67 NWs, 109 nanodisks, 155 and nano-islands with high shape anisotropy, 70 etc .). Due to their high sensitivity to changes in the magnetic properties of the interior of individual nanostructures and their user-friendly measurement environment conditions, they can be used for the measurement of such nanostructures as a matter of course.…”

Accessing low-energy magnetic microstates in symmetry-broken isolated square artificial spin ice vertices with magnetic field

“…The impact of defects or disorder via modifying the lattice constant, shape of nanomagnets in such ASI systems remains a field of intense research [7][8][9][10][11][12][13][14]. Investigating individual vertices allows detailed understanding of magnetization reversal [15,16]. As a natural extension of such ASI systems, creation of novel complex geometries such as sakthi [17,18], tetris [19], etc.…”