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Italian School of Magnetism Franca Albertini Istituto dei materiali per l’elettronica e il magnetismo (IMEM) del CNR, Parma Franca Albertini, IMEM-CNR Magnetic materials for energy

Magnetic materials for energy - Italian School on ...scuolaaimagn2016.fisica.unimi.it/lessons/Albertini.pdf · Magnetic materials for energy. ... Electric motor ... M=M S, H c>M S/2,

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Italian School of Magnetism

Franca Albertini

Istituto dei materiali per l’elettronica e il magnetismo (IMEM) del CNR, Parma

Franca Albertini, IMEM-CNR

Magnetic materials for energy

Magnetic materials for energy

Italian School of MagnetismFranca Albertini, IMEM-CNR

Production/Harvesting

Transmission/distribution

Conversion

Electric generatorElectric motor

Transformer

Mechanical to elctrical EElectrical to mechanical E Energy transfer

From N. Dempsey, ESM 2013

Magnetic field driven functional properties:magnetocaloric effect, magnetic shape memory, magnetic hyperthermia, magnetoresistance, magnetostriction…

Properties Exploitation

Functional magnetic materials

Franca Albertini, IMEM-CNR

Fingerprint

Soft magnetic materials:Trasformers, inductors, sensors

M

H

M

H

Hard magnetic materials:Field production: permanent magnets, magMEMS

Memories

Remote manipulation/sensing

Italian School of Magnetism

µµ00HHcc (T)(T)

10-3

10-5

5

Energy paradigms: renewable energy

Italian School of MagnetismFranca Albertini, IMEM-CNR

WORLD ENERGY

OUTLOOK 2016

Energy paradigms: emissions reduction

Franca Albertini, IMEM-CNR

Renewable energy sources

Energy efficient technologies WORLD ENERGY

OUTLOOK 2016

Italian School of Magnetism

Energy paradigms: closing loops

Redefining refuse as a resource

Franca Albertini, IMEM-CNR

NATURE 531 24 MARCH 2016

Italian School of Magnetism

Critical materials

Franca Albertini, IMEM-CNR Italian School of Magnetism

Italian School of MagnetismFranca Albertini, IMEM-CNR

Permanent magnets and hard magnetic materials

Permanent magnets: application sectors

Franca Albertini, IMEM-CNR

Motors and generators of electric and hybrid cars

Renewed scientific and technological interest

TWO NOTICEABLE EXAMPLES

Direct drive wind turbines

Italian School of Magnetism

Permanent magnets applications

Franca Albertini, IMEM-CNR Italian School of Magnetism

H

µ0MR µ0MS

B=µ0(H+M)

µ0HC

BHC

slope: -1(1-N)/N

BHmax

High Remanence, MR

High Coercive field, HC

High Maximum Energy Product, BHmax

Extrinsic properties(microstructure, texture, shape, domain structure)

High Saturation Magnetization, MS

High Magnetic Anisotropy,

Easy-axis system

High Curie Temperature

Intrinsic properties

Permanent magnets: requirements and properties

Franca Albertini, IMEM-CNR Italian School of Magnetism

Hc>MS

Breakthrough in the

‘50s: over the shape

barrier

BHmax (squared

loop) = 1/4 µ0MS2

Easy magnetization directions

Spin reorientation transitions

Uniaxial systemEMCA = K1 sin

2 θ + K2 sin4 θ + K3 sin

6 θ

EMCA = K1 sin2 θ + K2 sin4 θ + K3 sin6 θ + K3 'sin6 θ cos6φ

...)()( 2

3

2

2

2

12

2

1

2

3

2

3

2

2

2

2

2

110+++++= ααααααααα KKKE

MCA

Cubic Symmetry

Hexagonal symmetry

Uniaxial symmetry: bidimensional problem

)cossincossin(cossin 22

1

2242

21θθφφθθ KKKE

MCA++=

Franca Albertini, IMEM-CNR

Magnetic anisotropy - easy magnetization direction

Italian School of Magnetism

A simple case: uniaxial anisotropic system, non interacting singA simple case: uniaxial anisotropic system, non interacting single domains particles le domains particles

EMCA = K1 sin2 θ + K2 sin

4 θ + K3 sin6 θ EZ = −HMS cosγ

ETOT = EMCA + EZ

c-axisM

H

basal plane

θ1=γ+θ

Franca Albertini, IMEM-CNR

Coercivity is maximum in the easy direction

Anisotropy field: maximum limit of coercive field

Magnetic anisotropy – magnetization process

Italian School of Magnetism

HC in real materials: well below the intrinsic limit

Coercivity (Hc) in bulk magnets is a fraction (20-30% ) of the intrinsic upper limit (anisotropy

field, HA)

Microstructure plays a major role:

Texture

Polycrystalline character

Defects and secondary phases at grain boundaries

Local Reduction of exchange and anisotropy

Nucleation and pinning control the starting

and propagation of magnetization reversal

Appropriate microstructure: new optimized processing techniques

Franca Albertini, IMEM-CNR Italian School of Magnetism

Phenomenological treatment

Hard Magnetic Materials

Franca Albertini, IMEM-CNR Italian School of Magnetism

RE-TM intermetallic compounds

Rare earth

effective magnetic moment

Large Magnetocrystalline anisotropy

µeff = gµB J(J +1)

where J=L-S light RE

J=L+S heavy RE

Transition metal

High Curie Temperature

High Ms

Two-sublattice system

Excange coupling between RE and TM

CaCu5 parent structure

Franca Albertini, IMEM-CNR Italian School of Magnetism

Nd2Fe14B

Italian School of MagnetismFranca Albertini, IMEM-CNR

Compound Tc (K) µµµµ0MS(T) K1 (MJ/m3) Crit. single domain

size(nm)

Domain wall

width (nm)

Nd2Fe14B 585 1.6 5 1 214 4

Sm2Co17 1100 1.3 3.3 490 8.6

BaFe12O19 740 0.48 0.32 89 18

Easy-

magnetization

direction

tetragonal

Discovered in 1982

NdFeB – Dy substitution

Italian School of MagnetismFranca Albertini, IMEM-CNR

2 Kg of NdFe B in a hybrid veichle

600 Kg/MW in eolic generatorsHigh torque to weight ratio motors and generators:

fastly increasing demand of high temeperature application:

Partial replacement of Nd by DyO. Gutfleisch et al. Adv. Mat. 23 (2011) 821

Multiscale approaches

Advanced multiscale characterization techniques

Calculations: from the atomic to the micro and

macro scale

Combinatorial approaches

Thin films and nanoparticles as model systems

Materials for permanent magnets: challenges and strategies

Franca Albertini, IMEM-CNR

Intermediate performances

Dy, Tb elimination or reduction Microstructure control,

grain boundary engineering

Exchange coupled nanocomposites

New RE- free materials

Revisitation of materials (oxides, Mn-based),

Increase of the ratio TM/RE

RE- elimination

Y-La intermetallics

Microstructure control, grain boundary engineering

Reduction of Dy content

Diffusion of Dy in the outer shell of NdFeB

Grain size reduction and magnetic grain decoupling with nonmagnetic grain boundary phases

K. Hono et al. Scripta Mater 67 (2012), 530

Towards the elimination of heavy RE

H. Nakamura et al IEEE-TM 41 (2005) 3844

Nanometric Nanometric

dispersiondispersion of two

magnetic phases dsdh

BHBHmaxmax increase exploitable in PM applicationsincrease exploitable in PM applications

E.F. Kneller and R. Hawig,

IEEE T-M 27, 3588 (1991)

Echange-coupled nanocomposites

M=MS, Hc>MS/2, ideal squared hyteresis loop Artificially structured nanocomposite

Multilayer: lhard=2.4 nm, lsoft=9 nm BHmax = 1 MJ/m3

magnetisationhard + softsoft

anisotropy

Skomski’s prediciton: a 1MJoule magnet

Hard phase fraction= 9%; BHmax=1MJ/m3=137 KGOe

Sm2Fe17N3/Fe65Co35

R. Skomski, J. Appl. Phys.76 (1994) 7059

Exchange-spring

magnet regime

Italian School of MagnetismFranca Albertini, IMEM-CNR

Exchange-coupled nanocomposites

Control of the material structure at the nanoscale

Alignment of the esay anisotropy axes of hard phase

Ideal exchange coupling between grains

Nanocomposites

from

nanocrystalline

fine powders

prepared by

chemical methods

Fe50Co50

Fe65Co35

Fe80Co20

Several attempts were performed, but we are still very far from the predictions

A recent result on

SmCo7 phase

N. Poudyal et al Mater. Res. Express 1 (2014) 016103

Critical points:

Italian School of MagnetismFranca Albertini, IMEM-CNR

New materials: obtaining structural distorsion

MnBi, NiAs type hexagonal, thin films and bulk

Difficult to obtain as single phase

Fe-Ni, Tetragonal L10

slow kinetics formation

Template growth of

core/shell nanoparticles,

epitaxial thin films

Maogang Gong and Shenqiang Ren

Chem. Mater., 2015, 27 (22), pp 7795.

L10 FeNi—the mineral

“tetrataenite”—has been characterized using

specimens found in nickel-iron meteorites.

(NWA 6259 recovered from Northwest Africa

is 95 vol. % tetrataenite with a composition of 43 at. % Ni)

Interstitial αααα���� Fe16-N2 thin films and nanoparticles

Meatastable metal-metalloid Heuslers: a promising huge class of materials

SPD measurement

Sample from L. Lewis

Italian School of MagnetismFranca Albertini, IMEM-CNR

N. Demspey in “The magnetism roadmap 2014, J. Phys D Appl. Phys 47 (20014) 333001

The pull of stronger magnets

Italian School of MagnetismFranca Albertini, IMEM-CNR

Magnetocaloric materials and RT refrigeration

Italian School of MagnetismFranca Albertini, IMEM-CNR

The refrigeration scenario15% of total worldwide energy consumption involves the use of refrigeration and air

conditioning (IIR 2013): from <5% (temperate zones) up to 80% (tropical islands)

The large cities of developing countries are at tropical latitudes

Bangkok, Tailandia, 60 %

Delhi, India – 55%

Mumbai, India – 50%

Air conditioning demand is inceasing: By 2025, ~1 billion of new citiziens will become

“consumers”: their first purchase will be an air conditioner (McKinsey Global Initiative)

•New refrigeration technology based on the magnetocaloric effect

•Environment-friendly technology

High efficiency 30% higher than vapor compression

Elimination of harmful gases

Low noise

More compact, scalable

Magnetic refrigeration

Franca Albertini, IMEM-CNR

Adiabatic temperature change ∆Tad

( ) ∫

−=∆∆

2

1

),(

),(,

H

HHH

ad dHT

HTM

HTC

THTT

Magneto-thermodynamic effect of magnetic materials induced by the

application/removal of a magnetic field

Neglect pressure change (dp=0),

mechanical stress (dσ=0)

and electric field (dE=0)

Temperature (K)

En

tro

py (

J*K

g/K

)

0

H=0

Hmax

DST

max

0

( )

H H

T H HH

S M MS T dH

H T T

=

=

∂ ∂ ∂ = → ∆ =

∂ ∂ ∂ ∫

max

0

( )

i

x x

i

xxi xT

XS XS T dx

x T T

=

=

∂∂ ∂ = → ∆ =

∂ ∂ ∂ ∫

Maxwell relations

( , , , , ) + dG T H p E SdT MdH Vdp d PdEσ ε σ= − + + +

•Xi is the generalized

displacement (M, V, e, P)

•xi is the generalized force (H, p,

s, E)

i iSdT X dx= − +∑

magnetization discontinuity

MCE is maximum across magnetic transitions (Tc)

Isothermal magnetic entropy change ∆Sm

Equilibrium thermodynamics of reversible processes

Magnetocaloric effect

1881 E. Warburg discovers the magnetocaloric effect

(MCE) in pure Fe

1926-1927 P. Debye e W.F. Giauque suggest to use MCE to

refrigerate

1933 W.F. Giaque e D.P. MacDougall reach 0.25K

through adiabatic demagnetizaton of paramagnetic

salts.

1949

http://www.nobelprize.org/nobel_prizes/chemistry/laureates/194

9/giauque-lecture.pdf

1976 G.V. Brown: pioneeristic work on magnetocaloric effect at

room temperature (Gd) (1978 Los Alamos Steyert)

History

Franca Albertini, IMEM-CNR

1995-1998 K.A. Gschneidner Jr. @ Ames Lab and C.B. Zimm @ Astronautic

Corporation announce the results of their three-year project

Proof-of-priciple unit: it ran for over 5000 hours in 18 months

applied fied = 5T superconducting magnet

Wcool=600 W

Temperature span =10 K

Material: Gd spheres (5 Kg)

1997 K.A. Gschneidner’s group materials with “GIANT MAGNETOCALORIC” effect

V. K. Pecharsky et al. Journal of Alloys and

Compounds 344 (2002) 362–368

Magnetic field induces a structural phase

transition (from para M to Ferro O)

Morellon et al, Phys Rev B 58, (1998) R14 721

Magnetostructural transition

Recent history

General electrics &

Oak Ridge National Labs

First demnstrator,60W, 4-times more expensive than

conventonal refrigerator

20% energy saving

Claim: commercial product in 2020Haier, Astronautics & BASFLow cooling power Refrigerator(20K ∆T max)

Now

Lab scale prototypes

MC coolers: rotational working principleMC coolers: rotational working principle

Pros: Continuous operation, no dead volumes, no energy waste from alternate breaking-

acceleration of moving masses (typical defect of the linear reciprocating design)

Cons: difficult handling of the fluid heat transporter (fluid valves on rotating components)

Franca Albertini, IMEM-CNR

The ideal Magnetocaloric material should have:

High ∆S and ∆tad obtainable by permanent magnets(less than 2T)

Broad operating T range

Low hysteresis, highly eversible effect

Sustain many cycles (mechanical stability)

Be an excellent heat exchanger (fast dynamics)

Be stable on the long run (corrosion-free)

Rely on readily available, non-toxic, non-strategic chemical elements

Low cost large scale production

Magnetic refrigeration is a concerted scientific and technological problem

The effort for novel refrigerators relies on better materials

Materials: requirements and challenges

Franca Albertini, IMEM-CNR

MnAs, MnPGe: high ∆Smag, As replaced by

P and Ge. Low raw material cost,

difficult preparation route

Gd5(SiGe)4 high ∆Smag, ∆Tad high

raw material cost, difficult preparation route

La(FeSi): to increase Tc LaFeSiH

Low cost of raw materials, long term

stability issues for the hydrogenated phase

Ni-Mn-X Heusler alloys: high ∆smag,

∆Tad high

Wide possibility of tailoring order and

kind of transition, and type of

magnetocaloric effect: DIRECT-

INVERSEHysteresis losses and mechanical

stability issues

∆Tad values in a 2T field.From Liu et al. Nature Materials vol.11, p620 (2012)

MnFePSi: high reversible ∆Tad, low raw

material cost.

Towards commercialization

MnFe0.95P0.595B0.075Si0.33

Guillou et al. Adv. Materials 2014

MnFe0.95P0.595B0.075Si0.33

Liu et al. Nature Mater. 11 (2012) 623

Materials overview

Martensitic transformation

between the cubic L21 and a

lower symmetry structure

(5M IC monoclinic)

Magnetically ordered states

Ni.MnGa- the prototypical material

ΔM

Δχ

Conventional shape memory

Interplay between magneic and structural degrees of freedom

Ferromagnetic shape memory Heusler compounds

Martensitic transformation occurs between two phases showing remarkable differences in

the main properties

-structural properties

-magnetic properties

-electronic properties

�Small hysteresis (field, temperature, pressure, stress)

Entropy change

�Suitable martensitic-magnetic critical temperatures

�Volume change at the transformation dTM/dP

�Lattice distorsion dTM/dσ

Temperature

Magnetic field

Pressure

Stress

The transformation can be induced

�Magnetization change at the transformation dTM/dH Critical T can be

changed by applying

an external field

Ni2MnX (X=Ga, In, Sn, Sb) full Heuslers: Key properties

TTMM

280 320 360 400

Su

scep

tib

ility

(a.

u.)

Temperature (K)

220

275

330

385

2.05 2.1 2.15 2.2 2.25

Tra

nsit

ion

tem

pe

ratu

res (

K)

Composition

TC

TAM

TMA

a

TCm

1 2 3 4

2.1 2.2

Ni content (2+x), z=0

Cri

tical T

(K

)

Co-occurrence of magnetic and

structural transitions: first order

transition from low-symmetry

ferromagnet to high–symmetry

paramagnet300 320 340

Su

scep

tibili

ty (

a.

u.)

Temperature (K)

Tuning of critical T

Increase of the magnetization

change at the transformation

Tailoring martensitic and magnetic properties

Ni2+xMn1+yGa1+z

340 360 380

10

20

- ∆S

m(J

/kg K

)

T (K)

30

0300 320 340

0

2

4

6

8H=0- 1.6 T

T (K)

- ∆S

m(J

/kg K

)

4-time increase of the magnetic

entropy change

Franca Albertini, IMEM-CNR

Ni2MnGa shows a negative M

(saturation moment of austenite is lower

than the saturation moment of martensite)

Therefore,

Ni2Mn1.2Ga0.8

0MdT

dH>

0MT

∂ <∂

max

0

( ) 0

H H

HH

MS T dH

T

=

=

∂ ∆ = <

∂ ∫

Since field stabilizes the phase with higher

moment, TM shifts to higher temperatures

Direct MCE

Cooling by adiabatic demagnetization max0

0H

adT→

∆ >

Franca Albertini, IMEM-CNR

S. Fabbrici et al. J. of Entropy 16 (2014) 2204 and referenceces therein

By Co doping Mn-rich comounds: it is possible to tune magnetic & structural transtions:

number, order, nature (from ferro to para or from para to ferro on heating), and critical

temperatures

paramagnetic gap merging of structural and

austenitic TC

Ni50-wCowMn30+jGa20-jw=0, j=0

w=5w=9, j=2

w=5, j=0

j=2

separated

transitions

merging of

structural and

magnetic

transition (TcA)

TC-Martensite

Co-doped Ni-Mn-Ga Heuslers: a playground for magnetism and

structure

Franca Albertini, IMEM-CNR

Ni2Mn(In,Sb,Sn) (and (Ni,Co)2MnGa) show

positive ∆M

(saturation magnetization of austenite is

higher than the saturation magnetization of

martensite)

Therefore,

0MdT

dH<

0MT

∂ >∂

max

0

( ) 0

H H

HH

MS T dH

T

=

=

∂ ∆ = >

∂ ∫

Since field stabilizes the phase with higher

moment, TM shifts to lower temperatures

Inverse MCE

Adiabatic magnetizationmax0

0H

adT→

∆ <

Franca Albertini, IMEM-CNR

Direct versus inverse magnetocaloric effect

Franca Albertini, IMEM-CNR

Up to now the best Magnetocaloric performers among Heuslers

�Very weak Magnetic moment in

martensite

Coupled with:

�Very strong magnetic moment in

austenite

High ∆M and dTc/dH

Issue!!! Thermal hysteresis

Irreversible cooling!!

Ni 4

5,2

Co

5.1

Mn

36

.7In

13

Ni 4

9.8

Mn

35In

15

.2

Liu et al, Nature Mat. 11 (2012) p 620

Franca Albertini, IMEM-CNR

�Find the right composition:

structural compatibility

Z.

Zh

an

g e

t a

l. A

cta

Ma

ter.

57

(2

00

9)

43

32

�Exploit the multiple response to external

fields

0MdT

dH<

0MdTdp

>

Transformation matrix eigenvalue

λ2=1 means interface matching between

austenite and martensite

the transformation proceeds

through an invariant plane

Franca Albertini, IMEM-CNR

( , , , , ) + dG T H p E SdT MdH Vdp d PdEσ ε σ= − + + +

Barocaloric Electrocaloric

Magnetocaloric Elastocaloric

i iSdT X dx= − +∑

Planes et al, J Phys.: Condens. Matter 21 (2009) 233201

Magnetocaloric effect is one in a family of caloric effects

Thermal, elastic and magnetic variables

Franca Albertini, IMEM-CNR

Calorimetric measurements under hydrostatic pressure

Ni42.2Co8.4Mn32.4Ga15In2.1.

Direct barocaloric effect: |∆S| value larger than the

corresponding magnetocaloric values measured in 1T

Huge discontinuity of lattice parameters and

volume at the transformation

(∆V up to 1.2%, dP/dT up to -60 K/Gpa)Pressure/stress induced martensitic

transformation

Ll. Mañosa et al. Nature Mater. 9 (2010) 478

Milan-Solsona et al. APL 105 (2014) 241901

Barocaloric/elastocaloric effect

Barocaloric/elastocaloric effect

Franca Albertini, IMEM-CNR

Exploitation of magnetization variations

induced by T at the martensitic transformation

Ni45Co5Mn40Sn10

Diffusionless, fast and sharp

transition, small hysteresis,

high magnetization variation

-Magnetization variation due to stress induced martensitic transformation

-Flux variation due to moving parts: combined exploitation shape memory and magnetism

(Kohl, ICFSMA 2013, Boise)

Other harvesting mechanisms

Energy harvesting

Ferromagnetic shape memory materials for energy

Solid state refrigeration:

exploitation of giant caloric effects

(magneto-, baro- or elasto- caloric)

induced by the application of

magnetic field, pressure or stress

ON

OFF

FIELD

Smart applications Actuators, Sensors (temperature , fields pressure)

Energy harvesting

Crossing response of materials to different fields can be exploited

QUESTIONS?

ON

OFF

FIELD

THANK YOU FOR YOUR ATTENTION