#paramagnetism

Magnetic Field Maneuvers Magnetite Monolayers

An external magnetic field can bend and lift thin sheets of self-assembled nanoparticles. [...] Suppose you want to make a tiny robot to perform surgery inside a human patient. To avoid damaging healthy tissue and to squeeze into tight spots, the robot should be squishy. And manipulating the robot’s movements with magnetic fields would make sense, as tissues don’t respond to magnetism. But what material would you use for the robot’s limbs? Magnetic materials are stiff and brittle. Embedding tiny particles of them in a rubbery matrix could work, but the thinner—and therefore bendier—you make the composite material, the less it responds to a magnetic field. Heinrich Jaeger of the University of Chicago, Monica Olvera de la Cruz of Northwestern University, Illinois, and their collaborators have now overcome that obstacle by making thin, flexible sheets out of self-assembled nanoparticles of magnetite [1]. Even a modest field of 100 milliteslas can lift a sheet and bend it by 50°, they found.

Harnessing magnetic relaxation: 'Pac-Man effect' enables precise organization of superparamagnetic beads

Particles that are larger than regular molecules or atoms yet remain invisible to the naked eye can form a variety of useful structures, including miniature propellers for microrobots, cellular probes, and steerable microwheels designed for targeted drug delivery. Lisa Biswal's team of chemical engineers at Rice University has found that exposing a certain class of such particles—micron-sized beads endowed with a special magnetic sensitivity—to a rapidly alternating, rotating magnetic field causes them to organize into structures that are direction-dependent or anisotropic. This discovery is important because anisotropy can be adjusted to develop new, customizable material structures and properties.

A microscopic factory for small runners: New method uses magnetic loops for growth control

Researchers at the University of Bayreuth have developed a new method for controlling the growth of physical micro-runners. They used an external magnetic field to assemble paramagnetic colloidal spheres—i.e. only magnetic due to external influences—into rods of a certain length. Colloidal particles are tiny particles in the micro- or nanometer range that can be used in medicine as carriers of biochemicals. These so-called microscopic bipeds change their behavior of their own accord as soon as they are fully grown: They then decide to run away. No external intervention is necessary for this. Nevertheless, their behavior is not random, but follows the experimenters' plan. The research results have been published in Nature Communications. In this work, Jonas Elschner, Farzaneh Farrokhzad, Prof. Dr. Daniel de las Heras and Prof. Dr. Thomas Fischer from the Department of Experimental Physics at the University of Bayreuth have developed a microscopic factory for small runners: a biped factory.

Theoretical study shows that matter tends to be ordered at low temperatures

Classical phase transitions are governed by temperature. One of the most familiar examples is the phase transitions of water from solid to liquid to gas. However, other parameters govern phase transitions when temperatures approach absolute zero, including pressure, the magnetic field, and doping, which introduce disorder into the molecular structure of a material.

This topic is treated from the theoretical standpoint in the article "Unveiling the physics of the mutual interactions in paramagnets," published in Scientific Reports.

The paper resulted from discussions held in the laboratory in the context of the doctoral research of the two main authors, Lucas Squillante and Isys Mello, supervised by the last author, Mariano de Souza , a professor in the Physics Department of São Paulo State University's Institute of Geosciences and Exact Sciences (IGCE-UNESP) in Rio Claro, Brazil.

The other coauthors are Roberto Eugenio Lagos Mônaco and Antonio Carlos Seridonio , also professors at UNESP, and Harry Eugene Stanley, a professor at Boston University (USA).

How to Destroy a Magnet (+ interactive periodic table)

Magnetoelectric coupling in a paramagnetic ferroelectric crystal demonstrated

An international team of researchers at University of Montpellier, University of Aveiro and University of Coimbra has demonstrated magnetoelectric coupling in a paramagnetic ferroelectric crystal. In their paper published in the journal Science, the group describes the ytterbium-based molecular magnetoelectric material they discovered and its possible uses. Ye Zhou and Su-Ting Han with Shenzhen University have published a Perspective piece describing the work in the same journal issue.

Over the past two decades, scientists have been struggling to produce multiferroic materials. But as Zhou and Han note, despite an enormous amount of effort, researchers have been unable to create such materials that can be used at room temperature. And there have also been problems creating materials with strong enough coupling to be useful in commercial products. In this new effort, the researchers have created a material that might have the characteristics that scientists have been looking for.

Ferroelectricity is a property of certain materials that have an electric polarization that can be reversed by an external electric field. If an electric field is applied to such materials, their dipoles align resulting in polarization. Ferromagnetism is the high susceptibility of certain materials to magnetization. And as in ferroelectrics, if a magnetic field is applied, the material's electron spins are aligned, resulting in magnetism. In this new effort, the researchers created a material with electrical properties that change when exposed to a magnetic field instead of an electrical force at room temperature. The new material also achieves six polarization states by manipulation of the applied electric and magnetic fields.