Electric field control of magnetic moment in palladium

Researchers at the University of Tokyo and Central Research Institute of Electric Power Industry have successfully induced a magnetic moment in palladium (Pd), usually a non-magnetic material, and demonstrated the ability to reversibly control the strength of the magnet by applying an electric field ("Electric-field control of magnetic moment in Pd"). This research has demonstrated the possibility of electrically inducing magnetism in non-magnetic materials. Induced magnetic moment in palladium (Pd) by application of voltage. One possible mechanism to explain the increased magnetic moment is that, when a voltage is applied to the structure shown in the figure, charges within the palladium layer accumulate near the surface because the surface is covered by ions. (Image: Chiba Lab) If the properties of a material could be electrically tuned after production, it would be possible to easily obtain the desired functions when needed, further increasing the range of materials that could be used in magnetic devices. In fields that employ magnetic materials, tuning of magnetic force and control of magnetization direction (together, these properties are termed the “magnetic moment”) has been demonstrated by applying a voltage to a capacitor containing a magnetic film as one electrode and charging and discharging charge carriers (electrons) from the electrode. It is expected that this method will dramatically reduce power consumption compared to conventional means of controlling magnetic moment (heating, magnetic field or electric current application). Prior studies have reported that it is possible to erase the magnetic properties of a material by the application of an electric field. However, there are no reports of successfully inducing and cancelling magnetic properties in a non-magnetic material by the same method. The research group of Associate Professor Daichi Chiba at the University of Tokyo Graduate School of Engineering and the Central Research Institute of Electric Power Industry has shown that the strength of a magnetic moment induced in palladium, a metal which is usually non-magnetic, is electrically controllable, and that application of a positive voltage induces a stronger magnetic moment than a negative voltage. The research group fabricated an ultra-thin cobalt/palladium structure in which a ferromagnetically ordered magnetic moment was induced in the top palladium layer by the ferromagnetic proximity effect. The magnetic moment in this Pd layer was reversibly controlled by applying a voltage. “This offers a new avenue for making non-magnetic materials ferromagnetic,” says Associate Professor Chiba of this latest research. He continues, “If it becomes possible to easily and reversibly induce magnetic properties in a non-magnetic material by applying an electric voltage, we may be able to make use of many materials currently not used in the field of magnetic engineering and further increase the range of materials available for use in magnetic devices.”