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Young Researchers and Professionals
| Project leader |
Zivkovic Ivica |
| Administering organization: |
Institut za fiziku
P.P. 304
10000 Zagreb
Croatia
www.ifs.hr
Dr. sc. Milorad Milun, director |
| Partner Institution/Company: |
. |
| Grant type: |
3A |
| Project title: |
Magnetization of quantum magnets at ultra low temperatures |
| Project summary: |
The field of magnetism and magnetic materials is attracting a considerable
interest recently not only from the basic research community but also from the
application-driven studies. The investigations of new materials in the fields of
spintronics, magnetic semiconductors, novel superconductors, quantum phase
transitions and other exciting phenomena in magnetism offer the possibility to
answer some of the fundamental questions in nature. On the other hand, the
application of these materials holds a great potential in the development of new
memory elements, no-energy-loss transmission lines, quantum computers,
magnetic cooling, etc.
The fundamental observable which characterizes magnetic materials is the
magnetization and how it is changed when other control parameters (temperature,
magnetic field,...) are varied. The measurement of the magnetization can be
performed in several ways but the most sensitive method is using the SQUID
(Superconducting QUantum Interference Device).
Investigations of quantum magnets often require ultra low temperatures where the
influence of the thermal fluctuations is reduced and the dominant role is carried by
the quantum fluctuations. Those fluctuations can be tuned by other control
parameters (magnetic field, pressure,...) and give rise to quantum phase
transitions between different quantum ground states. An example of a well studied
quantum magnet is Li(Ho,Y)F4, where dipol-dipol interaction between holmium
moments gives rise to a very low ordering temperature and a rich phase diagram
when the holmium lattice is diluted with the nonmagnetic yttrium ions. However,
despite the extensive research, the systematic study of the magnetization is still
lacking.
Here we propose to develop a magnetometer based on the SQUID which will be
capable of measuring the magnetization at ultra low temperatures. With an
inventive use of materials to thermally decouple different parts of the system and
the piezo motor for the movement of the sample through the detection coils of the
SQUID, we plan to extend the standard temperature range for the SQUID-based
magnetometers by more than two orders of magnitude.
Other materials where quantum fluctuations are observed (single-molecule
magnets, low dimensional systems, geometrically frustrated systems) are already
investigated by several research groups in Zagreb. The extended temperature
range would greatly enhance the level of research conducted in them and it would
increase the competitiveness towards other research centers in the world. The
last but not the least, it would offer an opportunity to attract foreign researchers to
use this equipment for their projects thus allowing new ideas and new
collaborations to develop. |
| Hrvatski sažetak: |
Istaživanje magnetizm ai magnetskih materijala privlači značajnu pažnju ne samo od strane fundamentalnih istraživanja, nego i od od onih koja su orijentirana prema aplikacijama. Novi materijali u spintronici, magnetskim poluvodičima, kvantnim faznim prijelazima i ostalim uzbudljivim područjima magnetizma omogućavaju odgovore na neka od fundamentalnih pitanja o prirodi. S druge strane, aplikacije tih materijala u tehnologiji imaju veliki potencijal u razvoju novih memorijskih elemenata, štedljivih dalekovoda, kvantnih računala, magnetskih hladnjaka i tako dalje.
Osnovna veličina koja karakterizira magnetske materijale je magnetizacija i kako se ona mijenja kada se ostali kontrolni parametri mijenjaju (temperatura, magnetsko polje,...). Mjerenje magnetizacije se može izvesti na više načina, ali je najosjetljivija metoda gdje se koristi SQUID (supravodljivi kvantni interferencijski uređaj).
Istraživanja kvantnih magneta često zahtijevaju vrlo niske temperature gdje je smanjen utjecaj termalnih fluktuacija i dominantnu ulogu imaju kvantne fluktuacije. One se mogu kontrolirati kroz druge kontrolne parametre (magnetsko polje, tlak,...) što omogućava kvantne fazne prijelaze između različitih osnovnih kvantnih stanja. Primjer dobro istraženog kvantnog magneta je Li(Ho,Y)F4 gdje dipolna interakcija između holmijevih momenata dovodi do vrlo niske temperature uređivanja i vrlo bogatog faznog dijagrama kad se holmijeva rešetka razrijedi nemagnetskim ionom itrija. Unatoč tome, sustavno istraživanje magnetizacije do sada nije učinjeno.
Mi predlažemo u ovom projektu razvoj magnetometra baziranog na SQUID-u koji će biti u stanju mjeriti magnetizaciju na vrlo niskim temperaturama. Inventivnim korištenjem materijala različiti dijelovi sustava će se toplinski odvojiti, dok će se za prolazak uzorka kroz detekcijske zavojnice koristiti piezo motor. Na taj način će se temperaturni raspon SQUID-magnetometra proširiti za dva reda veličine.
Ostali materijali gdje su kvantne fluktuacije uočene (jednomolekularni magneti, niskodimenzionalni sustavi, geometrijski frustrirani sustavi) se već istražuju u nekoliko istraživačkih grupa u Zagrebu. Prošireni temperaturni raspon će značajno unaprijediti nivo istraživanja i povećat će kompetitivnost tih grupa u odnosu na ostale istraživačke centre u svijetu. Uz to, time se otvara mogućnost da se privuku strani istraživači da koriste tu opremu za svoje projekte te se na taj način potiče razmjena novih ideja i razvoj novih suradnji. |
| Amount requested from UKF: |
260.700 HRK |
| Amount of matching funding: |
52.200 HRK |
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