Electricity and magnetism coupled in new material, claim researchers

A magnet has a magnetic field, but no electric field, whilst a piezoelectric crystal can generate electric fields, but not magnetic fields. "Usually, both effects are created in very different ways," says Professor Andrei Pimenov. "Magnetic ordering comes from electrons aligning their magnetic moments, while electric ordering comes from positive and negative charges moving with respect to one another." In 2006, Prof Pimenov found evidence of excitations based on electric and magnetic ordering. These excitations, called 'electromagnons', have been debated by materials scientists, but Prof Pimenov and his team have succeeded in switching such excitations on and off with an electric field in a material made of dysprosium, manganese and oxygen (DyMnO3). In this material, many electrons align their magnetic moments at low temperatures. Each electron has a magnetic direction which is slightly distorted with respect to the adjoining electron – therefore the electrons create spiral of magnetic moments. The spiral has two possible orientations – clockwise or anticlockwise – and an external electric field can switch between these two possibilities. The effect can be demonstrated by sending terahertz radiation through the material: The polarisation of the terahertz beam is changed if the multiferroic material exhibits magnetic ordering. If the magnetic spiral in the material can be switched with an electric field, this electric field determines whether the polarisation of the terahertz beam is being rotated. According to the research team, the development could lead to new kinds of amplifiers, transistors or data storage devices, as well as highly sensitive sensors.