Magnetization Reversal Mechanism for CoFeB Ferromagnetic Nanotube Arrays

CoFeB nanotube arrays are fabricated in anodic aluminum oxide (AAO) membranes and track etched polycarbonate (PCTE) membranes by using an electrochemical method, and their magnetic properties are investigated by vibrating sample magnetometry. The coercivity H_c and remanent squareness S_Q of these CoFeB nanotube arrays are derived from hysteresis loops as a function of angle between the field and tube axis. The H_c(θ) curves for CoFeB nanotube arrays in AAO and PCTE membranes show M-type variation, while they change shape from M to mountain-type as the tube length increases. However, the overall easy axis perpendicular to tube axis does not change with tube length. The different angular dependences are attributed to different magnetization reversal mechanisms.