Is magnetism a chemical or physical property

15 For example, topographic, chemical, and magnetic information obtained from a thin iron film is shown in Figure 2. In recent work, we used circularly polarized radiation to explore local x-ray magnetic dichroism spectra with a tunneling tip. 9 Furthermore, our use of polarized x-rays provides the opportunity to probe the magnetic properties of a sample surface (in addition to gathering the elemental, chemical, and topographic information). For instance, we have achieved a lateral resolution of 2nm and a vertical resolution of a single atomic layer (i.e., the ultimate limit) at room temperature. With our developments and inventions we have realized a number of major advances and we have been able to demonstrate-see Figure 1(b)-direct elemental imaging, with atomic-scale sensitivity. (b) Simultaneously obtained topography and elemental contrast SX-STM characterizations of a nanoscale nickel (Ni) cluster on copper (Cu). The x-ray-induced currents are measured simultaneously at the tip (I TIP), shield (I SHIELD), and the sample (I SAMPLE) to provide the chemical contrast. The smart tip consists of a metallic core that tunnels over the sample surface, an insulating film to reduce the photoelectron background, and a conductive shield to prevent charging of the tip. Schematic illustration of the synchroton x-ray scanning tunneling microscopy (SX-STM) technique, where a smart tip is used as the detector and the tipвЂ“sample junction is illuminated by monochromatic synchrotron x-rays. In addition, to resolve the other two STM limitations-the transition of the tip from tunneling, into the far field 10 and the inherent convolution of the topography with the chemical information 11-we have invented a specialized topographic filter. As illustrated in Figure 1(a), our nanofabricated smart tips have a metalвЂ“insulatorвЂ“metal structure. To overcome the first problem (i.e., degradation of spatial resolution caused by electron ejection), we have developed specialized smart tips 8, 9 that limit the detection of x-ray-excited electrons to the very top of the tip apex. In our work, we have therefore developed a number of solutions to address the three issues associated with SX-STM. Last, the measured tip current is always a convolution of the conventional tunnel current (which is related to the sample topography) and the x-ray-excited electrons (which carry the material's chemical information). Second, because photoejected electrons still provide a deceptive current signal in the far field, the STM feedback system can lift the tip out of the tunneling regime without being noticed. First, electrons excited by x-rays do not just tunnel into the tip, but can also be ejected from the sample and hit the sidewalls of the tip detector (which degrades the spatial resolution). It is difficult, however, to achieve real chemical contrast because of three serious issues. The goal is to modulate the tunneling current through x-ray excitation and therewith obtain electronic and chemical contrast. A feedback system maintains a tipвЂ“sample separation that is typically less than 1nm. In this technique-which combines the chemical sensitivity of x-rays with the high spatial resolution of STM-a monochromatic x-ray beam is used to illuminate a tip-sample junction, while the tip makes raster scans across the sample surface. For many years, researchers have attempted to solve this problem by combining STM with synchrotron x-ray excitations, 4вЂ“7 and a new technique-known as synchrotron x-ray scanning tunneling microscopy (SX-STM)-has emerged. 3 STM also offers a finer degree of spatial resolution than almost any other image technique, but it is chemically вЂblindвЂ™ and thus cannot be used alone to directly identify chemical elements on a surface. Invented in the 1980s, scanning tunneling microscopy (STM) allows a large range of materials to be viewed at the atomic level. 1, 2 Although a variety of new x-ray nanoprobes and x-ray microscopy techniques have been developed in recent years, the spatial resolution of direct chemical or magnetic contrast imaging techniques remains on the order of several nanometers. This brings an acute necessity for direct chemical imaging of materials, i.e., with the use of x-ray microscopy at the nanometer and atomic length scales. The evolution of technology, however, currently points toward the miniaturization of devices and molecular motors, as well as the creation (through atomic manipulation) of new materials. Synchrotron light sources are extremely useful for the characterization of materials in many different research fields (including physics, chemistry, materials science, biology, medicine, geology, and cultural heritage).

Is magnetism a chemical or physical property