Magnetic Field Sensor (IMAGE) University of California - Berkeley Caption In the device, which is about the size of a fingernail, clusters of diamond nanocrystals (black spots) sit atop a material called a multiferroic. The multiferroic transmits microwave energy into the crystals much more efficiently than other methods. Credit Courtesy Dominic Labanowski Usage Restrictions with credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.