Materials Characterization at High Magnetic Felds and Extreme Temperatures: Focus on Magnetism

By Neil R Dilley

Birck Nanotechnology Center, Purdue University, West Lafayette, IN

Recent additions to the recharge center at the Birck Nanotechnology Center in Purdue’s Discovery Park include an MPMS‐3 SQUID magnetometer and a DynaCool Physical Properties Measurement System from Quantum Design. The MPMS‐3 measures the DC and AC magnetic moment of bulk, film or powder samples from 1.8 K – 1000 K and in applied fields up to 7 tesla. The system is also capable of simultaneous electrical excitation for magnetoelectric (multiferroic) investigations. Powered by a SQUID, it can achieve better than 10‐8 emu sensitivity which enables quantitative studies of ultrathin (<1 nm) films of magnetic materials. Magnetic anisotropy measurements are one common application for the MPMS‐3 (see figure). The DynaCool measures electrical, magnetic and thermal properties of samples down to 1.8 K and in applied fields up to 9 tesla. Being a general field/temperature platform, it is capable of adding customized probes, optical and RF measurements. The most popular measurement for the user group is magnetotransport (Hall effect, magneto‐resistance) of magnetic films and devices, sometimes utilizing the automated sample rotation insert. After reivewing the capabilities of the instruments, I will highlight some research results on both instruments including voltage‐controlled magnetic anisotropy, ferromagnetic resonance (FMR) spectroscopy, and finally magnetotransport with a look ahead to new high‐sensitivity electronics for carrier mobility detemination in low mobility systems.

Magnetic Microsystems: Tiny Magnets Solving Big Problems

By Donald P. Arnold, Electrical and Computer Engineering, University of Florida, Gainesville, FL

This talk highlights the development of microfabricated permanent magnets and their application in various functional microsystems. Basic concepts about magnets and physical scaling laws are introduced.  Two types of permanent magnet materials—electroplated layers and bonded powders—that overcome certain manufacturing and integration challenges are presented, along with the batch-fabrication process to create complex magnetic pole patterns in thick films, the method used to characterize the stray fields at the micro-scale, and they way these tiny magnets are being used for electromechanical transducers, nanomanufacturing, and microrobots.

Magnetic Nanowires: Revolutionizing Hard Drives, Random Access Memory, & Cancer Treatment

By Beth Stadler, Professor of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN  

Magnetic nanowires can have many names: bits, sensors, heads, artificial cilia, sensors, and nano-bots. These applications require nanometer control of dimensions, while incorporating various metals and alloys. To realize this control, 7- to 200-nm diameter nanowires are synthesized within insulating matrices by direct electrochemistry. Our nanowires can easily have lengths 10,000x their diameters, and they are often layered with magnetic and non-magnetic metals as required by each application. This talk will reveal synthesis secrets for nm-control of layer thicknesses, even for difficult alloys, which has enabled studies of magnetization reversal, magneto-elasticity, giant magnetoresistance, and spin transfer torque switching. 

Bio-sensing Summer Series 2010: Biomimetic Cilia Sensor Arrays Using Electrochemically Synthesized Magnetic Nanowires

By Beth Stadler, Professor of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN

Dynamics of Multimodal Magnetomotive Microspheres

By Adeel Ahmad, University of Illinois at Urbana-Champaign

Iron oxide magnetic nanoparticles (MNP’s), due to their small size, unique magnetic properties and the ability to manipulate these remotely, are promising materials for diagnostic, imaging, and therapeutics in biomedical applications. In this presentation, we describe the fabrication, characterization and some applications of protein-shell microspheres embedded with MNP’s in their cores. These magnetic microspheres have been functionalized to target the αvb3 integrin receptors that are known to be overexpressed in tumors and atherosclerotic lesions. An external magnetic field can be used to perturb these particles and the resultant displacements can be optically measured with nano-scale accuracy using magnet-motive optical coherence tomography (MM-OCT) to provide not only dynamic contrast in imaging but to also assess the biomechanical properties of the microenvironment. Preliminary results demonstrate tracking in vivo dynamics of these functionalized microspheres by using fluorescence imaging followed by ex vivo MM-OCT. Ongoing research includes studying the targeting and binding efficiency of these particles under flow conditions.