IAEA CRP: Ion Beam Modification of InsulatorsRCM, Dec. 10-14, 2007, FNRC, Uni. Chiang Mai, ThailandStudy of the formation of ferro-, para- and superpara-magnetic nano clusters by ion implantation itno suitable insulators

Principal investigators : Prof. K. Bharuth-Ram , University of KwaZulu-Natal, Durban and iThemba LABS, Faure. S. Africa

Prof. Dr. Hans Hofsaess, Universitaet Goettingen, Germany

+ Carsten Ronning, Peter Schaaf, Michael Uhrmacher, Uni-Goettingen. Terry Doyle, Cebo , iThemba LABS, South Africa.

+ Uli Wahl: Emission channeling Gerd Weyer et al., MS following Mn57 implantation

IntroductionNanoclusters of Fm atoms have high proportion of surface atoms increase spin magnetic moment towards high spin limit reduction in effective quenching of the orbital magnetic moment.

+ quantum size effects + modified valence electron screening

Novel properties: magnetic moments enhanced by up to 35% superparamagnetic behaviour in clusters below a critical size magnetic behaviour in non-FM transition metals

Applications in ultra-high recording magnetic recording media, information and telecommunications technology.

Achieved already by ion implantation at doses of 1017 cm-2. - due to accumulation at extended lattice sites? or diffusion and agglomeration of implanted ions?

Objective:Investigate the implantation parameters required to achieve magneticnano-clusters, i.e. energy and dose, sample temperature and annealing characteristics,

Methods includeTemperature dependent Moessbauer spectroscopy and magnetization measurements, to determine the size of clusters and their magnetic properties.

RBS and Raman Spectrometry, MOKE, UV-VIS Transmission Spectrometry -- to determine implantation profile and complex formation in the host matrix.

Reported on in June 2006:

Implant of 57Fe at E = 60 keV, at Uni-Goettingen to a dose of 5 x 1015 cm-2 .

Substrates: 3C-SiC, CVD diamond, graphite Moessbauer spectroscopy (at UKZN) at RT and LN2 on 3C-SiC sample: as-implanted sample, and after annealing at 400 C.

Moessbauer spectroscopy (at Uni-Goettingen) after annealing at 600 C VSM on as-implanted and after annealing at 600 C on 3C-SiC sample

MOKE and Raman Spectroscopy on as- implanted and after annealing at 400 C and 600 C: CVD and 3C-SiC samples

Results: Mossbauer MeasurementsMossbauer measurements were made with a approx. 8 mCi source (30 mCi in May 2003).Each spectrum at RT, has > 10 million events, accumulated over 4 weeks.At LN2, longer measurement time was required.

MOKE Measurements (Magneto-Optical Kerr Effect)a) As implantedb) TA = 900 K

VSM Measurements(TB Doyle, UKZN) SiC(Fe) sample , Virgin SiC, HolderVSM measurements only possible after acquisition of a bipolar power supply for magnet, obtained in 2005 as donation from the Alexander von Humboldt Stiftung.

Plot shows average of data collected during many measurements over several months (TB Doyle).

We are at the limit of resolution of the device, but a small ferromagnetic effect is noticeable.

Raman Spectroscopya) CVD diamond as-Implantedb) CVD diamond annealed at 900 Kc) 3C-SiC sample annealed at 900K

There is evidence of ferromagnetic and paramagnetic ordering, but data with better statistics is required.

So, Plans for 2007 included:i) obtaining new, stronger Moessbauer Sources (50 mCi)

ii) Increasing the concentration of Fe in the samples,

iii) investigating implantation induced magnetization effects in other substrates.

Early in 2007, enriched 57Fe pellets were purchased, and implantation into 3C-SiC, CVD diamond, ZnO, SiO2 and graphite were undertaken at 60 and 80 keV energy, and up to a fluence of 1 x 1016/cm2 (at Goettingen).

Two 50mCi MS sources ordered, eventually delivered in Oct. 2007

Measurements from end October : CEMS, TMS.

SubstrateFluence(x1016/cm2)Temp(K)MOKE RBSRaman UV-VISMOSS VSMCVD0.50

1.00RT600CRTY YY Y Y YYYY 3C-SiC0.50

1.00RT400CRT300C

Y Y

Y YY YY YYYGraphite0.050.50ZnO0.50

1.0RT

RT325C

Y Y

Y Y

YYSiO20.50

1.00RT

RT

Y

Y

SAIP 2007

Hyperfine Interactions and Measurables1. Isomer Shift2. Magnetic interactionEmag = - m . BEmag = mI . g mN. Bz d = k (rabs rref)( ), lattice site, charge state3. Electric Quadrupole Interaction

RBS Measurements2 MeV 4He+Grazing angle = -10O

UV-VIS Transmission3C-SiC: virgin and implanted region i) as implanted, ii) Annealed at 350C.2. ZnO: Implanted regions i) as implanted ii) Annealed at 350 C.

3C-SiC1 x 1016/cm2

SiO2

ZnOas Impl.TA= 350 C

Moessbauer MeasurementsCVD Diamond:

Magnetization measurements ??? -- merger of UDW and UN UKZN - School of Physics (and Fac. of Science) to Westville campus

VSM equipment dismantled and still in boxes!!!

Moessbauer Studies following 57Mn implantation

57Mn57CoECb137 keV14.4 keV, 98 ns0CE57Fe5/2-3/2--1. 57Co source: 30 mCi + Typical dose: 5 x 1014 57Fe tm ~ 14 days lattice damage

2. In-beam MS CE and recoil implant 57Fe* tm ~ 24 36 hrs Dose < 1010 cm-2. teff = t .

3. 57Mn* implantation Dose < 1013 cm-2. b decay 57Fe* Erecoil = 40 keV

tm~ 10 min.

At ISOLDE, CERNMass separated 57Mn* accelerated to 60 keV,and implanted into sample held at temp T.

14.4 (+DE) keV gammas detected in PPAC, mounted directly on to MDU.

Production of radioactive ion beams at ISOLDE, CERN.

3C-SiC

Graphite

Components:S1 : Single lineD1: defect doubletSx1 : sharp FM sextetSx2 & Sx3: Broad sextets with Eq interaction.

Effect is reversible. due Fe-V-O complex??

Conclusions1. The lighter mass substrates ( SiC, SiO2) hold greater promise.

2. After implantation to a fluence of 1 x 1016 / cm2 indications of magnetically split components in Moessbauer spectra this fluence gives Moessbauer spectra with acceptable statistics higher dose implantation with Fe-56 other fm species (Mn, Co) non-fm species (Na, C)

ACKNOWLEDGEMENTS

IAEA Wulf Rosenberg and Francoise MullhauserHans Hofsaess, Uli wahl and colleagues in GoettingenYu Liangden and FNRC, Chiang Mai UniversityThe Group generally.

Thank You