Sebastian Fähler, IFW Dresden

Program committee: � Jürgen Eckert, IFW Dresden� Gunther Eggeler, Ruhr U. Bochum� Heike Emmerich, U. Bayreuth� Peter Entel, U. Duisburg-Essen� Stefan Müller, U. Bonn� Eckhard Quandt, CAU Kiel� Karsten Albe, TU Darmstadt

Caloric Effects in Ferroic Materials: New Concepts for Cooling

SPP 1599

www.FerroicCooling.de

DFG:� Burkhard Jahnen

3

Program today

12:30 Lunch at the cafeteria of the IFW Dresden

13:30 Introduction to SPP 1599, S. Fähler, IFW Dresden Chair

14:00 Talks:

B. Jahnen (DFG), O. Gufleisch (IFW Dresden), M. Acet (U

Duisburg-Essen), O. Gutfleisch (IFW Dresden), A. Ludwig

(Ruhr-U Bochum), A. Nayak/ G. Winterlik/ C. Felser (U

Mainz), S. Wurmehl (IFW Dresden), A. Waske/ N. Mattern/ J.

Eckert (IFW Dresden), H. Wende (U Duisburg-Essen)

GuntherEggeler

15:45 Coffee Break

16:20 Talks:

V. Shvartsman (U. Duisburg-Essen), W. Skrotzki (TU

Dresden), A. Böhm (Fraunhofer IWU), E. Quandt (CAU Kiel),

G. Eggeler/ O. Kastner (Ruhr-U Bochum), S. Seelecke/ A.

Schütze (U des Saarlandes), A. Raatz (TU Braunschweig), P.

Entel (U Duisburg-Essen), T. Hickel (MPI Düsseldorf), M.

Gruner/ P. Entel (U Duisburg-Essen), U. Rößler (IFW

Dresden), L. Kienle (CAU Kiel)

Heike Emmerich

20:00 Dinner at the Pulverturm at the Frauenkirche

4

Program tomorrow

Chair

09:00 Talks:

S. Scudino/ U. Kühn/ J. Eckert (IFW Dresden), Y. Luo (U

Göttingen), A. Hütten (U Bielefeld), S. Fähler (IFW Dresden),

M. Kohl (KIT-IMT), T. Lampke/ T. Halle (TU Chemnitz), M.

Wagner (TU Chemnitz), H. Emmerich (U Bayreuth)

EckhardQuandt

10:20 Coffee Break

10:50 Talks:

J. McCord (CAU Kiel), C. Melcher (RWTH Aachen), I. Opahle

(Ruhr-U Bochum), D. Hägele (Ruhr-U Bochum), K. Albe (TU

Darmstadt), L. Eng (TU Dresden), A. Schönecker (Fraunhofer

IKTS Dresden), K. Albe (TU Darmstadt), D. Rytz (FEE GmbH

Idar-Oberstein)

Jürgen Eckert

12:30 Concluding remarks and discussion, S. Fähler, IFW

Dresden

13:00 Lunch at the cafeteria of the IFW Dresden

14:00 Internal meeting of the programme committee

5

Preliminary timeline SPP 1599

11/2011 Public call for proposals9.3.2012 Deadline for submission of proposalsSummer 2012 EvaluationAutumn 2012 Start of project

6

apply magnetic field

remove magnetic field

releases heat

absorbs heat

Magnetocaloric effect

H

� Adiabatic removal of field shifts entropy from lattice to magnetic subsystem

� Second order transition at Curie temperature

H

2nd order

7

1st vs. 2nd order transformation

1st order:� Huge entropy change� Hysteresis loss

2nd order:� Broad working temperature

V. K. Pecharsky, K. A. Gschneidner,

Phys. Rev. Lett. 78 (1997) 4494

8

releases heat

absorbs heat

Magnetocaloric effect

DEVpuMHSTUG ∆+∆+∆+∆−∆−∆=∆ σ

M>>0

M=0

M>>0

M=0

1st order

apply magnetic field

remove magnetic field

9

Elastocaloric Effect

releases heat

absorbs heat

DEVpuMHSTUG ∆+∆+∆+∆−∆−∆=∆ σ

apply stress

remove stress

10

releases heat

absorbs heat

Barocaloric Effect

DEVpuMHSTUG ∆+∆+∆+∆−∆−∆=∆ σ

compression decompression

11

releases heat

absorbs heat

Electrocaloric Effect

DEVpuMHSTUG ∆+∆+∆+∆−∆−∆=∆ σ

apply electric field

remove electric field

12

Length scales involved

Electronic structure

Crystal structure

Micro-structure

Device structure

cmÅ

13

Scale bridging modeling

Electronic structure

T-dep. DFT

MolecularDynamics

Multiphysicsfinite elements

cmÅ

Phase Field

14

Connecting time and length scales

Spin-lattice coupling

Interface movement

Fatigue

yearsfs

Heat conduction

15

Which material is best?

� Intrinsic properties

– Huge latent heat

– High susceptibility to external fields (large ∆M, ∆V, ∆u, ∆D)

– TM around room temperature (tunable)

� Extrinsic properties

– Low hysteresis

– Cycle stability

� Technological issues

– Cost (Fe-based, FeRh )

– Environmentally friendly (Pb, As)

16

How to quantify ferroic cooling?

� Indirect measurements of ∆S by Maxwell relation

– Not valid for 1. order phase transition

– Hysteresis requires complex measurement protocol

Caron et al. J. Mag. Mag. Mat. 321 (2009) 3559

– Can result in spurious “giant” effects due to reorientation

Niemann et al, ArXiv: 1110.3617

� Use direct measurement of ∆T

17

Which approach is most applicable?

Magnetocaloriceffect

N S

+ −

+ −+ − + −+ −

+ −+ −Electrocaloriceffect

Elastocaloriceffect

Barocaloriceffect

Toroidalcaloriceffect?

Multicaloric

effects

→→→→ Towards a unified description

18

� Summing up entropy changes of lattice, spin…

� Tuning of working temperature

� Use of actuation properties to establish heat transfer

Multicaloric effects

TM< RT

stress stress

TM≈ RT

e. g. Stress induced martensite

H=0 H>0

+ + +…+ −

+ −+ − + −+ −

+ −+ −

19

From ferroic materials towards cooling systems

� Faster heat exchange

� Reduced conduction losses

� Generation of sufficient driving fields

� Innovative cooling system designsS. J. Lee, et al., J. Appl.

Phys. 91, 8894 (2002)

Freestanding films

Chmielus et al. Nat.

Mat. 8 (2009) 863

Foam Films

Niemann et al.

APL. 97

(2010) 222507

20

Collaborations

� Apply for joint projects (up to 4 partners)� Bilateral collaborations

� Before submission:– Send semi-public 1-2 page project description until 1.12.2011– Will be distributed per email to all who submitted description– Updates every month

21

Dinner 8 p.m.

-> An der Frauenkirche 12, 01067 Dresden

22

Modern society relies on the possibility to cool below ambient.

Ll. Manosa, ICOMAT 2011

23

Summary

� Which scheme is most efficient for solid state refrigeration? � Which length scales are involved?� What is the correlation between time and length scales?� Which are the best materials?