Hi, I am doing research in Hall Mobility and Half-heusler compounds. I've taken some data on several samples now and I am kind of perplexed. We use a very stable magnetic field between -.6 Tesla and .6 Tesla to do the measurements. Currently we take data points at intervals of .1 tesla to acquire a line of Magnetic Field vs. Resistance (or voltage since Current is held constant). And for the most part we take the slope of that line to get a "B / R" ratio and then calculate the carrier concentration. Most of the samples have run smoothly and we've gotten linear data, but a few of the samples are returning Parabolic data. This meaning that we start at .6 Tesla and go to -.6 Tesla in .1 Tesla increments. Taking data at each point. http://img682.imageshack.us/img682/2230/graph3t.png" [Broken] We are also using a Van der pauw geometry instead of bar geometry (due to the shape of the samples that are made). my question is, What does a parabolic curve mean for Hall effect data. I thought it should be mostly linear. If you need any more info that I've left out, just ask I should be able to tell you. Thanks.