Using Bulk Superconductors
Scientists Create Portable,
High-Field Magnet Systems
It is now possible for scientists to use high magnetic fields to exploit the magnetism of a material
for controlling chemical and physical processes.
Superconductors are materials that carry large electrical currents with little or no resistance when cooled
below a certain cryogenic temperature.
The current carried by a superconductor
also generates a magnetic field and a
magnetized bulk superconductor—which
is similar in appearance to an ice hockey
puck—can be used as a super-strength,
quasi-permanent magnet, generating fields
of several Tesla.
In 2014, the Bulk Superconductivity
Group in the Department of Engineering,
University of Cambridge, broke a world
record by trapping 17. 6 tesla in a stack of
two bulk, high-temperature superconductors
at 26 K, leapfrogging the previous record
of 17. 24 tesla at 29 K that stood for over
a decade. This was recognized by the
Guinness World Records in 2016. This
is an order of magnitude higher than the
1. 5-2 tesla limit for applications using
conventional permanent magnets (PMs),
such as neodymium magnets (Nd-Fe-B),
making these materials extremely attractive
for a number of engineering applications
that rely on high magnetic fields, including
compact and energy-efficient motors/
generators with unprecedented power
densities and portable magnetic resonance
imaging (MRI) and nuclear magnetic
resonance (NMR) systems.
Furthermore, compared with
electromagnets (copper-wound or
superconducting), no direct, continuous
connection to a power supply is necessary
and the size of the magnet to provide the
same field is considerably smaller. Figure 1
shows a comparison of the magnetic field
available from a conventional PM, a bulk
superconductor and an electromagnet,
and the mechanism by which each magnet
generates its magnetic field.
It is now also possible for scientists to
use high magnetic fields to exploit the
magnetism of a material for controlling
chemical and physical processes, which
is attractive for magnetic separation and
magnetic drug delivery systems (MDDS),
for example. Such applications rely on the
force exerted on a magnetic particle that
By Mark Ainslie, PhD, University of Cambridge
Figure 1: A comparison of the magnetic field available from a conventional permanent magnet, a bulk superconductor and an electromagnet, and the mechanism by which each magnet
generates its magnetic field. Credit: Mark Ainslie
