Micromechanical force detectors for measuring magnetization at high magnetic fields and the magnetic~ response of Ba3Cr2O8.

We report magnetization measurements of Ba3Cr2O8 using micromechanical faraday balance magnetometers. The magnetometers consist of a movable polysilicon plate (500 by 500 micrometers) supported~ by four springs 2.75 micrometers above a fixed electrode. When small samples of the magnetic material are placed at the center of the movable plate, the natural gradient of the field creates a force on the sample that changes the capacitance between the plate and electrode, while the response to magnetic torque is minimized. The absolute magnetization of the sample can be determined provided that the magnetic field gradient is known. The device is used to measure the magnetization of a small sample of Ba3Cr2O8 with mass of 1 microgram. At high fields, our measurements reveal an asymmetric dome like structure in the temperature-magnetic field phase diagram, possibly related to the Bose-Einstein condensation of spin triplet degrees of freedom.