High performance tubular GMI sensors
Arrays of rolled-up on-chip-integrated giant magneto-impedance (GMI) sensors equipped with pick-up coils are demonstrated. The geometrical transformation of an initially planar layout into a tubular 3D architecture stabilizes favorable azimuthal magnetic domain patterns. This work creates a solid foundation for further development of CMOS compatible GMI sensorics for magnetoencephalography.
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All-electric access to the magnetic-field-invariant magnetization of antiferromagnets
Antiferromagnets have the potential to revolutionize spintronics due to their inherently magnetic-field stable magnetic order. To reveal the rich physics of these materials, we introduce spinning-current anomalous Hall magnetometry opening the scope for magnetic phenomena that can go amiss otherwise. This provides new insights into the physics of the fundamentally-appealing magnetoelectric Cr2O3 and application-relevant IrMn antiferromagnets. The work was carried out in collaboration with the HZB, BESSY II.
This work was chosen as PRL Editors' suggestion
Magnetism in Möbius rings
In physics of nanomagnetism curvature-induced magnetic effects are subject of exciting current topical studies. In this framework we demonstrate that the magnetic Möbius ring is a unique object because it unites two classes of geometrical effects, namely, topologically induced magnetization patterning and curvature induced chirality symmetry breaking. With this work we complete the broad theoretical studies of various physical phenomena related to the Mobius geometry by including magnetic phenomena. This work was carried out in close collaboration with the Taras Shevchenko National University and the Bogolyubov Institute for Theoretical Physics in Kiev, Ukraine.
Magnetic sense for everybody
We have developed an electronic skin with a magneto-sensory system that equips the recipient with a “sixth sense” able to perceive the presence of static or dynamic magnetic fields. These novel magneto-electronic sensors are less than two micrometers thick and weigh only three gram per square meter. They withstand extreme bending with radii of less than three micrometer, and survive crumpling like a piece of paper without sacrificing the sensor performance. These ultrathin magnetic sensors with extraordinary mechanical robustness are ideally suited to be wearable, yet unobtrusive and imperceptible for orientation and manipulation aids. This work was carried out in close collaboration with the University of Tokyo and Osaka University in Japan.
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Transfer printed stretchable magnetoelectronics
A novel fabrication method for stretchable magnetoresistive sensors is introduced, which relies on the transfer of a complex microsensor system prepared on common rigid donor substrates to prestretched elastomeric membranes in a single step. This direct transfer printing method boosts the fabrication potential of stretchable magnetoelectronics in terms of miniaturization and level of complexity, and provides strain-invariant sensors up to 30% tensile deformation.
Domain patterns of magnetic rolled-up microtubes
Rolled-up magnetic microtubes display spiral-like, longitudinally or azimuthally magnetized domain patterns. The rolled-up geometry offers an elegant possibility for tailoring the fundamental magnetic interactions at the nanoscale in three-dimensions. The novel magnetic-domain patterns have a strong impact on their magnetic response and transport properties and could be attractive for future magnetoimpedance-based field sensors.
Stretchable magnetoelectronic devices are demonstrated for the first time. We fabricated GMR multilayers as well as spin valves on free-standing elastic Poly(dimethylsiloxane) (PDMS) membranes. The GMR performance of the sensors on rigid silicon and on free-standing PDMS is similar and does not change with tensile deformations of up to 29% revealing a top sensitivity of 0.8 %/Oe in a magnetic field of 12 Oe. Stretchable magnetoelectronics generates a new quality to modern interactive application fields like smart skin and flexible consumer electronics equipped with magnetic functionalities.
M. Melzer et al., Adv. Mater. 24, 6468 (2012) URL PDF
M. Melzer et al., Nano Lett. 11, 2522 (2011) URL PDF
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Advances in Engineering (April 22, 2013) URL
Magnetically capped rolled-up nanomembranes
In this work, we address curvature-driven modifications of magnetic properties in confined cylindrically curved magnetic nanomembranes. The curved architectures are prepared by capping non-magnetic micrometer- and nanometer-sized rolled-up membranes with a soft-magnetic 20 nm thick permalloy (Ni80Fe20) film. Due to the curvature-driven thickness gradient in magnetic nanostructures, magnetic stray field merely exists at the longitudinal edges of the cap. The corresponding anisotropy of magnetostatic interaction (along with respect to across the cylindrical cap) allows to reduce interaction between neighboring magnetic nanostructures still preserving vortex state, which is a bottleneck of planar stripes. Thus, a much higher areal density of magnetic wires compared to planar stripes might be achieved, which is beneficial to increase storage density of racetrack memory devices.
We fabricated the first printable magnetic sensor that relies on the giant magnetoresistance effect (GMR). The magnetic ink can be painted on virtually any substrate such as paper, polymers, ceramics, glass and exhibits a room-temperature GMR of up to 8%. The performance of a printable GMR sensor is demonstrated by integration into a hybrid electronic circuit produced on the paper of a postcard. The operation of a light emitting diode (LED) is triggered by a permanent magnet that modifies the resistance of the printable magnetic sensor and alters the current flow through the LED. Our demonstrator with a magnetic switch printed on a postcard suggests paves the way for interactive and fully printable electronics.
This work was highlighted in:
- Nanowerk (July 19, 2012) URL PDF
- Spectrum IEEE (July 20, 2012) URL PDF
- Bild (August 29, 2012) URL PDF
- Pro-physik (August 29, 2012) URL PDF
- Uni aktuell at TU Chemnitz (August 29, 2012) URL PDF
- Wissenschaftler (August 31, 2012) URL PDF
- PREVIEW Event & Communication (September 3, 2012) URL PDF
- Wissenschaft Aktuel (September 4, 2012) URL
- Paper of the month: The Latest Science (September 3, 2012)
- Advances in Engineering (April 16, 2013) URL
Elastic magnetic sensor with isotropic sensitivity for in-flow detection of magnetic objects
We present a conceptually new approach for the detection of magnetic objects flowing through a fluidic channel. We produce an elastic and stretchable magnetic sensor and wrap it around a capillary tubing. Thus, the stray fields induced by the flowing magnetic objects can be detected virtually in all directions (isotropic sensitivity), which is unique for the elastic sensor compared to rigid planar counterparts. In combination with magnetic particles as biomarkers, this elastic magnetic sensor can be considered as a new generation of biosensors for cells or even biomolecules evading many difficulties of traditional optical detection methods like low speed, excitation, bulky and expensive equipment, biomolecular amplification and the need for transparent packaging.
Magnetic microhelix coil structures
We design and investigate three-dimensional microhelix coil structures that are radial-, corkscrew-, and hollow-bar-magnetized. The magnetization configurations of the differently magnetized coils are experimentally revealed by probing their specific dynamic response to an external magnetic field. Helix coils offer an opportunity to realize microscale geometries of the magnetic toroidal moment, observed so far only in bulk multiferroic materials.
Rolled-up magnetic sensor for in-flow detection of magnetic objects
Rolled-up nanotech is used to fabricate magnetic sensor devices, which are directly integrated into fluidic architectures. Strain engineering is applied to roll-up a thin layer stack revealing giant magnetoresistence (GMR). In this way, the rolled-up tube acts as a fluidic channel, while the integrated GMR sensor responds to a magnetic field. In-flow detection of ferromagnetic CrO2 nanoparticles embedded in a biocompatible polymeric hydrogel shell is highlighted. The advantage of rolled-up devices is their integrability into existing on-chip technologies and the ability to combine several functions into a single architecture, possibly leading to a fully operational lab-in-a-tube system.
First magnetic rolled-up microtubes demonstrated
Magnetic rolled-up microtubes are fabricated for the first time, and their hysteresis curves are measured. The tubes consist of semiconductor/magnetic radial superlattices rolled up from a thin solid hybrid material film. The magnetic properties reflect the change of symmetry adopted by the film, once it forms into a cylindrical structure.
Towards flexible magnetoelectronics
Strongly enhanced GMR on flexible substrates is reported for Co/Cu multilayers deposited on plastics by introducing a photoresist buffer layer. GMR values of Co/Cu multilayers on buffered flexible substrates are even larger than those on thermally oxidized Si substrates due to an increased antiferromagnetic coupling fraction. The GMR effect can be easily tuned mechanically by substrate stretching.