Directional Behavior of Remanent Magnetizations at Low Temperatures

许多天然磁性矿物在低温下发生转变。研究地球磁场历史的科学家有时会利用这种转变来帮助岩石消磁，消除岩石形成后获得的磁化。例如，磁铁矿在大约120 K时经历晶体结构的变化（从斜方晶系到单斜晶系），称为Verwey转变。在转变过程中还观察到较大的磁铁矿颗粒所携带的剩磁的损失。然而，我们对这一过程的理解，以及与其他天然磁性矿物中的转变相关的过程，迄今为止主要是基于对总磁矩的测量。一个原型设备，使测量方向与SQUID磁强计在冷却/升温通过低温过渡提出有趣的现象，可能与磁畴壁和晶体偏转的相互作用。PI将测试这一假设，汇编关于各种磁性矿物的新的方向数据，并继续开发用于低温冷却/方向分析的设备。这项工作的更广泛影响包括教育工作和对岩石磁学和古磁学社区有用的研究工具的开发（以及对低温下磁性感兴趣的物理学专业）。本科生将参与磁性矿物的表征，低温剩磁测量和数据分析。

Many natural magnetic minerals undergo transitions at lowtemperature. Scientists investigating the history of Earth'smagnetic field sometimes use such transitions to help demagnetize rocks,removing magnetizations acquired after rock formation. For example,magnetite undergoes a change in crystal structure (from orthorhombic tomonoclinic) at approximately 120 K known as the Verwey transition. Aloss of the magnetic remanence carried by relatively large magnetitegrains is also observed at the transition. However, our understanding ofthis process, as well as processes associated with transitions in othernatural magnetic minerals, has to date been based mainly on measurements oftotal magnetic moment. A prototype device enabling the measurement ofdirections with a SQUID magnetometer during cooling/warming throughlow temperature transitions suggests interesting phenomena,possibly related to the interactions of magnetic domain walls andcrystal deflects. The PI will test this hypothesis, compile new directionaldata on a wide range of magnetic minerals, and continue to develop the devicefor low temperature cooling/directional analysis. Broader impacts of thework include educational efforts and the development of a research tooluseful for the rock magnetism and paleomagnetism communities (and thecommunity in physics interested in magnetic properties at low temperatures).Undergraduates will take part in the characterization of magneticminerals, low temperature remanence measurements and data analyses.