Single pulse calibration of magnetic field sensors using mobile 43 kJ facility

In this work we present a mobile 43 kJ pulsed magnetic field facility for single pulse calibration of magnetic field sensors. The magnetic field generator is capable of generating magnetic fields up to 40 T with pulse durations in the range of 0.3–2 ms. The high power crowbar circuit is used for the reverse voltage protection and pulse shaping purposes. The structure, the development challenges and the implemented solutions to improve the facility for the calibration of the magnetic field sensors are overviewed. The experimental data of the application of the proposed generator for the calibration of manganite magnetic field sensors are presented

Single Pulse Calibration of Magnetic Field Sensors Using Mobile 43 kJ Facility

In this work we present a mobile 43 kJ pulsed magnetic field facility for single pulse calibration of magnetic field sensors. The magnetic field generator is capable of generating magnetic fields up to 40 T with pulse durations in the range of 0.3-2 ms. The high power crowbar circuit is used for the reverse voltage protection and pulse shaping purposes. The structure, the development challenges and the implemented solutions to improve the facility for the calibration of the magnetic field sensors are overviewed. The experimental data of the application of the proposed generator for the calibration of manganite magnetic field sensors are presented

Collective formation of misfit dislocations at the critical thickness

The critical thickness constitutes a vital parameter in heterostructure epitaxy engineering as it determines the limit where crystal coherency is lost. By finite element modeling of the total strain relaxation in finite size heterostructure nanowires, we show that the equilibrium configuration changes abruptly at the critical thickness from a fully elastically strained structure to a structure with a network of MDs. We show how the interdependent MD relaxation changes as a function of the lattice mismatch. These findings suggest that a collective formation of MDs takes place when the growing heterostructure layer exceeds the critical thickness.Comment: 7 pages, 4 figures main, 4 pages, 4 figures supplementa

Experimental setup for magnetoresistance analysis of lanthanum manganites thin films

A measurement and automation equipment for measuring the manganite resistance dependence on magnetic field is designed and developed in this work. Equipment consists of the electromagnet, the programmable power source, the magnetic field meter and the resistance measurement device. All devices are connected to PC by the GPIB cables and the GPIB-USB converter. The control program was created by using the LabVIEW software package. It enabled to change the steps of the current through the electromagnet in different ranges of the magnetic field and to set desired measurement accuracy and duration. The system was used for measuring of the magnetoresistance of the manganites films dependence on the magnetic field. The accuracy, which was achieved using this equipment, allows calculating anisotropy of MR of the manganites films despite to small changes of the resistance at low magnetic field

Computer controlled thermostat for the resistivity measurements of the La1-xSrxMnO3 thin films

The temperature stabilization system for the magnetoresistance measurements of the La1-xSrxMnO3 manganites is described in this paper. The thermostat cell with the Peltier heating/cooling element was manufactured specially to be placed between the poles of the electromagnet. The heat sink attached to the rear side of the Peltier element is cooled by the flowing tap water. Platinum film temperature probe was used for the temperature feedback signal. Universal multimeter “Tektronix DMM 4050” was used as a temperature meter and a regulated laboratory power supply “TTI QL 564P” was used to supply the current through the Peltier element. Both instruments were controlled by the computer software via the USB and GPIB interfaces. The software implementing a PID algorithm was written in the LabView graphical programming interface. The results show that the temperature of the sample can be changed in 2-3 minutes depending on the temperature step and is kept constant with precision of ±0.02 °C

Theoretical analysis of the strain mapping in a single core-shell nanowire by x-ray Bragg ptychography

X-ray Bragg ptychography (XBP) is an experimental technique for high-resolution strain mapping in a single nano- and mesoscopic crystalline structures. In this work we discuss the conditions that allow direct interpretation of the ptychographic reconstructions in terms of the strain distribution obtained from the two dimensional (2D) XBP. Simulations of the 2D XBP experiments under realistic experimental conditions are performed with a model of InGaN/GaN core-shell nanowire with low (1%) and high (30%) Indium concentrations in the shell. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

First x-ray nanoimaging experiments at NanoMAX

NanoMAX is a hard x-ray nanoimaging beamline at the new Swedish synchrotron radiation source MAX IV that became operational in 2016. Being a beamline dedicated to x-ray nanoimaging in both 2D and 3D, NanoMAX is the first to take full advantage of MAX IVs exceptional low emittance and resulting coherent properties. We present results from the first experiments at NanoMAX that took place in December 2016. These did not use the final experimental stations that will become available to users, but a temporary arrangement including zone plate and order-sorting aperture stages and a piezo-driven sample scanner. We used zone plates with outermost zone widths of 100 nm and 30 nm and performed experiments at 8 keV photon energy for x-ray absorption and fluorescence imaging and ptychography. Moreover, we investigated stability and coherence with a Ronchi test method. Despite the rather simple setup, we could demonstrate spatial resolution below 50 nm after only a few hours of beamtime. The results showed that the beamline is working as expected and experiments approaching the 10 nm resolution level or below should be possible in the future

Fast Strain Mapping of Nanowire Light-Emitting Diodes Using Nanofocused X-ray Beams

X-ray nanobeams are unique nondestructive probes that allow direct measurements of the nanoscale strain distribution and composition inside the micrometer thick layered structures that are found in most electronic device architectures. However, the method is usually extremely time-consuming, and as a result, data sets are often constrained to a few or even single objects. Here we demonstrate that by special design of a nanofocused X-ray beam diffraction experiment we can (in a single 2D scan with no sample rotation) measure the individual strain and composition profiles of many structures in an array of upright standing nanowires. We make use of the observation that in the generic nanowire device configuration, which is found in high-speed transistors, solar cells, and light-emitting diodes, each wire exhibits very small degrees of random tilts and twists toward the substrate. Although the tilt and twist are very small, they give a new contrast mechanism between different wires. In the present case, we image complex nanowires for nanoLED fabrication and compare to theoretical simulations, demonstrating that this fast method is suitable for real nanostructured devices