Download presentation
Presentation is loading. Please wait.
1
Non-equilibrium dynamics in superspin glass systems
D. Peddis and D. Fiorani Institute of Matter of Structure (ISM) National Research Council (CNR) Roma - Italy SIF 2015
2
david.peddis@ism.cnr.it– SIF 2015
Magnetic Materials: The dimension is very important permanent micron nanoparticles clusters molecular individual magnets particles clusters spins S = 10 20 10 8 6 5 4 3 2 magnetic moment multi - domain single - domain SIF 2015
3
From Multi to mono-domain structure
A= Exchange energy density K = Anisotropy energy constant Material dc (nm) Fe 15 Co 35 -Fe2O3 30 SmCo5 750 Kittel_PRB_1946 SIF 2015
4
CoFe2O4 Nanoparticles (TEM image)
C. Cannas, D. Peddis et al Chem Mater. 2010 SIF 2015
5
Biomedical Applications ( MRI, drug delivery)
Supermagnetism Strong interactions Eint>>Ea Collective magnetic state Weak interactions Ea(tot) = Ea +Eint Eint<<Ea Modified SP Superferromagnetism (SFM) Super spin glass (SSG) Interparticle interaction energy (Eint) Biomedical Applications ( MRI, drug delivery) SIF 2015
6
david.peddis@ism.cnr.it– SIF 2015
Introduction SIF 2015
7
D. Peddis et al Chem Mater 2013
Introduction Frustration Randomness SuperSpin Glass Spin Glass S. Nakameae, Thesis T<Tg D. Peddis et al Chem Mater 2013 SIF 2015
8
david.peddis@ism.cnr.it– SIF 2015
SG/SSG SIF 2015
9
david.peddis@ism.cnr.it– SIF 2015
MnFe2O4 SIF 2015
10
david.peddis@ism.cnr.it– SIF 2015
Structural characterization Oil Water NsDABS SEM <D> XRD (nm) 2 Surface Area (m2/g) 278 TEM <D> BET (nm) 4 SIF 2015
11
Interparticle Interactions
Id (DCD remanent magnetization after saturation) Ir ( IRM remanent magnetization after demagnetization) M Plot M < demagnetizing interaction M = 0, no interaction M > magnetizing interaction ICSM 2014
12
david.peddis@ism.cnr.it– SIF 2015
M Vs.T : ZFC FC Tmax _ZFC (K) 45.3 (3) Tmax _FC (K) 43.1 (3) Tirr (K) 50.0 (2) Tirr/Tmax _ZFC 1.1 SIF 2015
13
Measurement done in Uppsala D. Peddis, D. Fiorani, et al. in prep
MnFe2O4 SuperSpinglass Power law 0 4.210-13 Tg 45.3 (3) α 8.6 (2) SG systems Measurement done in Uppsala (P. Nordblad. R Mathieu) D. Peddis, D. Fiorani, et al. in prep SIF 2015
14
david.peddis@ism.cnr.it– SIF 2015
Mössbauer Spectroscopy TBM (K) Mössbauer 62 m (s) 510-9 TmaxZFC(K) SQUID 45 m (s) SIF 2015
15
david.peddis@ism.cnr.it– SIF 2015
16
D. Peddis, D. Fiorani, et al. in prep
MnFe2O4 SuperSpinglass Power law 0 1.910-12 Tg 45.3 (3) α 8.6 (2) SG systems SIF 2015 D. Peddis, D. Fiorani, et al. in prep
17
T>Glassy Temperature
SG/SSG: Non equilibrium dynamic (NED) T>Glassy Temperature T =T’(<Tg; dT/dt0) T =T’ (<Tg dT/dt0) SIF 2015
18
david.peddis@ism.cnr.it– SIF 2015
Aging Measurements (ZFC) H = 0 H =10 Oe 150 K 5 K H = 10 Oe 5 K 60 K ZFC reference curve H = 0 H =10 Oe 150 K 20 K tw= 3 h 5 K H = 10 Oe 5 K 60 K ZFC memory curve SIF 2015
19
david.peddis@ism.cnr.it– SIF 2015
Aging Measurements (TRM) H = 10 H =0Oe 150 K 5 K H = 0 5 K 60 K TRM reference curve H = 10 H =0 Oe 150 K 20 K tw= 3 h 5 K H = 0 Oe 5 K 60 K TRM memory curve SIF 2015
20
First evidence of principle of superposition for superspin glass
SG systems R. Mathieu, PRB, 2001 SIF 2015
21
M. Bellusci, et al , Polymer Intern, 2009
MnFe2O4 nanoparticles + Albumin Aqueous dispersion of the ferrite and albumin SIF 2015
22
david.peddis@ism.cnr.it– SIF 2015
MnFe2O4 FM SIF 2015
23
david.peddis@ism.cnr.it– SIF 2015
Samples FM Nps AFM Matrix Substrate PEEK 25 μm Buffer Layer Ag Ǻ Film ------ 2000 Ǻ Capping Layer Ǻ FM NPs Diamag. matrix C. Binns (Leicester, UK) Cluster source MBE source SIF 2015
24
david.peddis@ism.cnr.it– SIF 2015
Co Nps Mn Matrix Substrate PEEK 25 μm Buffer Layer Ag Ǻ Film ------ 2000 Ǻ Capping Layer Ǻ Co NPs Ag matrix Log-normal distribution of particle size (measured in situ by a quadrupole filter) C. Binns (Leicester, UK) 1.8 nm 280 atoms SIF 2015
25
david.peddis@ism.cnr.it– SIF 2015
Exchange bias effect ZFC FC Co/CoO TN < T < TC T < TN H SIF 2015
26
Devices governed by Interface Exchange Coupling
HARD DISK Magnetoresistive read heads MRAMs Spin valve structure SIF 2015
27
david.peddis@ism.cnr.it– ICSM 2014
Co Nps Mn Matrix Substrate PEEK 25 μm Buffer Layer Ag Ǻ Film ------ 2000 Ǻ Capping Layer Ǻ Co NPs Ag matrix Log-normal distribution of particle size (measured in situ by a quadrupole filter) C. Binns (Leicester, UK) 1.8 nm 280 atoms ICSM 2014
28
david.peddis@ism.cnr.it– SIF 2015
ZFC FC Measurements H = 100 Oe assembly of non interacting particles Superparamagnetic behaviour: Tmax 17 K Curie-law behaviour of c (FC) Tirr/Tmax = 4.7 like behaviour Tmax of c(ZFC): 65 K Plateau of c(FC) below 30 K Tirr/Tmax = 1.2 SIF 2015
29
david.peddis@ism.cnr.it– SIF 2015
AC Measurements (n = 0.3 – 30 Hz) (n = 0.3 – 30 Hz) Arrhenius law t = t0exp(KaV/KbT) t0 = 6x10-11s Ka=2x107erg/cm3 Power law t = t0 [Tg/(Tmax(n)) – Tg)]a a = 8.2; Tg = 62 K; t0 = 10-9 s In SG 7 < a < 9 SIF 2015
30
Non-Equilibrium dynamic (NED)
H = 0 H =100 Oe 150 K 5 K H = 100 Oe 5 K 80 K ZFC reference curve H = 0 H =100 Oe 150 K 50 K Tw= X 5 K H = 100 Oe 5 K 80 K ZFC memory curve SIF 2015 D. Peddis et al, JPCS; 2010
31
M. Vasilakaki, K.N. Trohidou, D. Peddis, et al , PRB 2013
NED: MonteCarlo Simulation M. Vasilakaki, K.N. Trohidou, D. Peddis, et al , PRB 2013 SIF 2015 D. Peddis et al, JPCS; 2010
32
NED: Interface Exchange coupling
Without Dipolar Interaction with Interface exchange coupling without Dipolar Interaction Without Interface exchange coupling M. Vasilakaki, K.N. Trohidou, D. Peddis, et al , PRB 2013 SIF 2015
33
M. Vasilakaki, K.N. Trohidou, D. Peddis, et al , PRB 2013
NED: Role of exchange Bias M. Vasilakaki, K.N. Trohidou, D. Peddis, et al , PRB 2013 SIF 2015
34
david.peddis@ism.cnr.it– SIF 2015
Exchange Bias and SSG 30 K SIF 2015
35
Summary MnFe2O4 Co@Mn (VVF 4.7%)
Dynamical properties in a wide range of frequencies Principle of superposition (NED) Role of IEC in NED SSG and EB SIF 2015
36
david.peddis@ism.cnr.it– SIF 2015
D. Fiorani. E. Agostinelli, CNR, Rome, Italy A.M.Testa, G. Varvaro, S. Laureti, E. Patrizi, N. Domingo CNR* –Spain C. Binns, S. Baker Univ. of Leicester, UK J. Blackmann Univ. of Reading, UK P. Trohidou, M. Vasalikaki Demokritos, Athens, Greece P. Nordblad, R. Mathieu, M. Hudl Uppsala University SIF 2015
37
M. Vasilakaki, K.N. Trohidou
Monte Carlo Simulation M. Vasilakaki, K.N. Trohidou SIF 2015
38
david.peddis@ism.cnr.it– SIF 2015
Monte Carlo SIF 2015
Similar presentations
