Planar Hall sensors for micro-Hall magnetometry

Abstract

In this work we present a new method to fabricate planar Hall sensors from GaAs–AlGaAs heterojunctions, which can be used to examine the local stray field at a specific section of a micron-sized magnet. Instead of mesa etching we implanted oxygen ions with an energy of 1.5 keV which deplete the two-dimensional electron gas underneath the exposed areas but leave the wafer flat. Planar double Hall cross devices were employed to investigate 30 nm thick electroplated Ni rings with outer and inner diameters ranging from 1.2 to 2 μm and from 0.3 to 1.6 μm, respectively. By comparing the signals from both Hall crosses of the sensor, we can distinguish between local stray field variations and changes of the global magnetization pattern. A hysteresis loop measured at a temperature of 110 K suggests that magnetization reversal occurs via a magnetic vortex structure.

Single-Particle Phenomena in Magnetic Nanostructures

“…As an example, we can consider the study, by Rahm et al [176], of a nanoring deposited on the top of a double Hall device. The Ni ring has inner and outer dimensions of 0.3 and 1.2 μm, respectively.…”

“…One important consideration for the micro-Hall sensor is that the sample must be smaller than the geometrical area of the active region of the device. One method of ensuring a good sample/sensor geometry is using the implantation of oxygen ions into the GaAs/AlGaAs heterojunction, which helps to define the effective geometric shape of the Hall sensor [176]. 2 The magnetic nanostructure is then deposited on top of the Hall sensor, as illustrated in Fig.…”

Incorporating fluorescent dyes and quantum dots into magnetic microbeads for immunoassays

“…For example, giant magnetoresistive (GMR) (815) and Hall sensors (16,17) are two magneto-electronic devices that can be used to sense the weak magnetic fields generated by a magnetic microbead. Although such devices can be sensitive to single beads, the sensors are complicated to fabricate, and their use for quantitative detection requires magnetically monodispersed beads.…”

Rotational dynamics of paired nano-domain walls confined in an elliptical ring

“…In the present work, we have studied rotational dynamics of the domain walls in a ring structure under a linearly oscillating in-plane magnetic field. The goal of the study is to achieve a unidirectional rotation of the paired domain walls (head-head and tail-tail) in so-called onion states and develop a prototype of a ''domain wall motor''.It is well known that there are two stable magnetic states in a ring structure, onion state and closure state [1][2][3][4][5][6][7]. Under a sufficiently strong in-plane magnetic field, paired domain walls are nucleated in the direction along the inplane magnetic field.…”

“…It is well known that there are two stable magnetic states in a ring structure, onion state and closure state [1][2][3][4][5][6][7]. Under a sufficiently strong in-plane magnetic field, paired domain walls are nucleated in the direction along the inplane magnetic field.…”