national high magnetic field laboratory
PULSED FIELD FACILITY
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Multiferroics combine electric and magnetic ordering in the same material. When these two properties are coupled, then a magnetic field can control the electric polarization, and an electric field can control the magnetization. This can lead to new applications such as ultra-sensitive solid state magnetic sensors, computer memory that combines the best properties of ferroelectric storage and magnetic read/write, solid-state microwave and high-power devices, energy harvesting, and other novel and smart circuit devices.
Fast and high pulsed magnetic fields at the National High Magnetic Field Laboratory allow very sensitive measurements of multiferroic properties, in particular the electric polarization as function of magnetic field down to fractions of a pC/cm2. The speed of the pulse actually increases signal to noise compared to measurements in superconducting magnets. Magnetic fields up 100 T are available. Samples are measured in a helium environment down to 0.5 K. Dielectric constant can also be measured in dc magnetic fields to 20 T and in pulsed fields up to 60 T in the mid or long-pulse magnets using a capacitance at frequencies up to 50 kHz.
Rough schematic of electric polarization setup. If the sample (green) has a net electric polarization, charge is drawn out of ground onto the capacitor plates (orange) to compensate. As the polarization changes, it induces a current, which is read by the ammeter (actually a low input-impedance current-to-voltage converter). This is in turn integrated to find the electric polarization. A typical short pulse magnet field pulse is shown above as well on the right.
Multiferroics are insulating materials where charge, spin, and lattice degrees of freedom can be coupled together to create new multifunctional materials, a type of spintronics that does not dissipate heat.
a) Sample data showing pC/cm² resolution on the organo-metallic material CuCl₂-2SO(CH₃)₂. [Zapf et al, PRB 82, 060402(R), (2010)] b) Data from arXiv:1105.2058. on Lu₂MnCoO₆. c) High magnetic field transitions in the electric polarization of another multiferroic material captured in the electric polarization.