Magnetocaloric and magnetovolume effects in Fe-based alloys

Pablo Alvarez Alonso

Department of Material Science and Metallurgic EngineeringUniversity of Oviedo

4 July 2011

P. Alvarez (University of Oviedo) MCE and magnetovolume effects in Fe-based alloys 04/07/11 1 / 48

Outline

1 IntroductionMagnetocaloric EffectMagnetovolume AnomaliesR2Fe17 alloysFeZrBCu amorphous alloys

2 Experimental TechniquesFabricationStructural and Magnetic Characterization

3 ResultsMagnetovolume Anomalies and Magnetocaloric effect of R2Fe17 compoundsMagnetocaloric Effect in Pseudobinary AxB2 -xFe17 alloysMagnetic Properties and Magnetocaloric Effect of Fe-based amorphous alloys

4 Conclusions

Outline

4 Conclusions

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4 Conclusions

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4 Conclusions

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4 Conclusions

Magnetocaloric effectOrigin

Magnetocaloric EffectDefinition and Theory

Total Entropy ofMetallic Gd underTwo AppliedMagnetic Fields.

Adiabatic TemperatureChange (∆Tadi ) of Gd

Magnetic EntropyChange for GdAl2

Maxwell RelationIsothermal Magnetic Entropy Change

∆SM (T ,H2)P,∆H =

∫ H2

(∂M∂T

∆SM (T ,H2)P,∆H =

∫ H2

(∂M∂T

∆SM (T ,H2)P,∆H =

∫ H2

(∂M∂T

∆SM (T ,H2)P,∆H =

∫ H2

(∂M∂T

Magnetocaloric EffectMagnetic Refrigeration: Principles and Applications

Applications

ConsumerI Air conditioningI DehumidifiersI RefrigeratorsI Motor refrigerators

CommercialI Vending machinesI Cooling drinksI Cold storeI Exhibitors &

Showcases

ElectronicsI Active cooling of

electronic circuits

MedicineI Magnetic resonance

imagingI Portable coolers

ScienceI Gas liquefactionI Cryogenics

Adventages

Less energyconsumption

High cooling efficiency

Environmental friendly

Low maintenancecosts

Large durability andstability

No mechanicalvibrations

Magnetocaloric EffectMagnetic Refrigeration: Principles and Applications

Applications

ConsumerI Air conditioningI DehumidifiersI RefrigeratorsI Motor refrigerators

CommercialI Vending machinesI Cooling drinksI Cold storeI Exhibitors &

Showcases

ElectronicsI Active cooling of

electronic circuits

MedicineI Magnetic resonance

imagingI Portable coolers

ScienceI Gas liquefactionI Cryogenics

Adventages

Less energyconsumption

High cooling efficiency

Environmental friendly

Low maintenancecosts

Large durability andstability

No mechanicalvibrations

Magnetocaloric EffectRelative Cooling Power

Relative Cooling Power(RCP)

Estimation of RCP

RCP1(H) = |∆SPeakM (H) | × δTFWHM

RCP2(H) =

∫ TH

TC|∆SM (T ,H)| dT .

RCP3(H) = max{∣∣∆Smag (T1,H)

∣∣× (T2 − T1)}

Combination of δTFWHM and ∆SPeakM

Broad ∆SM → Large RCP

RCP (5 T) for Metallic Gd

RCP1 = 687 Jkg−1

RCP2 = 503 Jkg−1

RCP3 = 402 Jkg−1

P.Gorria et al., J. Phys D: Appl. Phys., 41 (2008)192003 (5pp)

Magnetocaloric EffectRelative Cooling Power

Relative Cooling Power(RCP)

Estimation of RCP

RCP1(H) = |∆SPeakM (H) | × δTFWHM

RCP2(H) =

∫ TH

TC|∆SM (T ,H)| dT .

RCP3(H) = max{∣∣∆Smag (T1,H)

∣∣× (T2 − T1)}

Combination of δTFWHM and ∆SPeakM

Broad ∆SM → Large RCP

RCP (5 T) for Metallic Gd

RCP1 = 687 Jkg−1

RCP2 = 503 Jkg−1

RCP3 = 402 Jkg−1

P.Gorria et al., J. Phys D: Appl. Phys., 41 (2008)192003 (5pp)

Outline

4 Conclusions

Magnetovolume Anomalies

Lattice Parameters a andc, and the cell volume Vvs T for Sm2Fe14B

Magnetovolume anomalies: Coupling betweenthe crystal lattice and the magnetism

Extrapolation from the Non-OrderedStateGruneisen relation

αnm (T ) =κΓCp (T )

Magnetostriction

λa = (a− a0)/a0

λc = (c − c0)/c0

ωS = (V − V0)/V0

Lattice Parameters a andc, and the cell volume Vvs T for Sm2Fe14B Magnetovolume anomalies: Coupling between

the crystal lattice and the magnetism

Magnetostriction

λa = (a− a0)/a0

λc = (c − c0)/c0

ωS = (V − V0)/V0

Lattice Parameters a andc, and the cell volume Vvs T for Sm2Fe14B Magnetovolume anomalies: Coupling between

the crystal lattice and the magnetism

Magnetostriction

λa = (a− a0)/a0

λc = (c − c0)/c0

ωS = (V − V0)/V0

Outline

4 Conclusions

R2Fe17 alloysCrystal Structure

Rhombohedral Th2Zn17-type (R3m space group)

YCePrNdSmGdTbDy

Fe1(6c): <<Dumm-bell site>>Oriented along the c-axis

Hexagonal Th2Ni17-type (P63/mmc space group)

dTbDyHoErTmYbLuY

Fe1(4f): <<Dumm-bell site>>Oriented along the c-axis

YCePrNdSmGdTbDy

Hexagonal Th2Ni17-type (P63/mmc space group)GdTbDyHoErTmYbLuY

YCePrNdSmGdTbDy

R2Fe17 alloysMagnetovolume Anomalies and Magnetocaloric Effect in R2Fe17 alloys

Magnetovolume Anomalies: Causes

Dumb-bell sites

{DFe−Fe 6 2.45 A → Negative exchange InteractionsDFe−Fe ≥ 2.45 A → Positive exchange Interactions

Magnetovolume Anomalies: Effects

{Anomalous thermal expansionNegative pressure dependence of TC

Magnetic PropertiesR2Fe17 alloys exhibit SOPT

TC arround RT

Large MS

Magnetocaloric Effect in R2Fe17 alloys

H. Chen et al., JM3

320 (2008) 1382-1384

Dumb-bell sites

TC arround RT

Large MS

H. Chen et al., JM3

320 (2008) 1382-1384

Dumb-bell sites

TC arround RT

Large MS

H. Chen et al., JM3

320 (2008) 1382-1384

Outline

4 Conclusions

FeZrBCu amorphous alloys

∆SM(T ) for Nanoperm alloys

V. Franco et al., J. Appl. Phys. 100 (2006) 064307

Fe-content variation of TC forNanoperm alloys

P. Alvarez et al., Intermetallics 18 (2010)2464-2467

Magnetic and Magnetocaloric PropertiesBroad Second Order Magnetic Phase Transition

Tunnable Curie Temperatures in the RT Regime

Moderate values of MS

Outline

4 Conclusions

Fabrication

Arc Furnace Melt Spinner

Furnace Ball-Mill

Outline

4 Conclusions

CharacterizationStructure and Microstructure

Electronic Microscopies (University of Oviedo)

Scanning (JEOL JSM-6100) Transmission (JEOL 2000 EX-II)

Diffraction

X-ray (University of Oviedo) Synchrotron (ESRF: ID27) Neutron (ILL: D1A, D1B, D2B, D4)

CharacterizationMagnetic Characterization

VSMUniversity of Sevilla

PPMSUniversity of OviedoUniversity of CantabriaIPICYT

SQUIDUniversity of CantabriaSlovak Academy of Science

Outline

4 Conclusions

Magnetovolume Anomalies and Magnetocaloric Effect of R2Fe17compoundsCrystal and Magnetic Structure

XRPD patterns forRhombohedral andHexagonal R2Fe17alloys

NPD pattern below and overTC

FerrimagneticStructure

Magnetic StructurePr2Fe17, Nd2Fe17 and Y2Fe17 → Collinear Ferromagnetic

Gd2Fe17, Tb2Fe17, Dy2Fe17, Ho2Fe17, Er2Fe17 and Tm2Fe17 → Collinear Ferrimagnetic(Tm2Fe17 Spin Reorientation at 100 K)

Ce2Fe17 and Lu2Fe17 → Complex Magnetic Behavior

NPD pattern for the Dy2Fe17 alloy

Rhombohedral Dy2Fe17Ferrimagnetic (TC = 363 K)

Thermo-Diffraction experiments

Er2Fe17 Magnetic Moments Tb2Fe17 Magnetic Moments

Thermo-Diffraction experiments

Er2Fe17 Magnetic Moments Tb2Fe17 Magnetic Moments

Magnetovolume Anomalies and Magnetocaloric Effect of R2Fe17compoundsMagnetovolume Anomalies

VCell (T ) for Rhombohedral and Hexagonal R2Fe17 alloys

Extrapolation V(T)

Linear and Volume Magnetostriction

λa = (a− a0)/a0

λc = (c − c0)/c0

ωS = (V − V0)/V0

Comparation between ωS and MFe

λa = (a− a0)/a0

λc = (c − c0)/c0

ωS = (V − V0)/V0

λa = (a− a0)/a0

λc = (c − c0)/c0

ωS = (V − V0)/V0

Lattice Parameters a and cvs Pressure for Dy2Fe17 andEr2Fe17 alloys- RT

V vs T for Er2Fe17 alloy

First-Order Birch-MurnaghanEquation of State

)−7/3−(

)−5/3]

P(V ) curve for the Gd2Fe17 alloy

)−7/3−(

)−5/3]

)−7/3−(

)−5/3]

M vs T under Pressure for Pr2Fe17compound

dTCdP ≈ −4 K/kBar

M vs T under Pressure for Tm2Fe17compound

M vs T under Pressure for Pr2Fe17compound

M vs T under Pressure for Tm2Fe17compound

Magnetovolume Anomalies and Magnetocaloric Effect of R2Fe17compoundsMagnetocaloric Effect

M vs (T ,H)

∆SM(T ) for Rhombohedral andHexagonal R2Fe17 alloys(µ0H = 0 − 5 T)

M vs (T ,H)

∆SM(T ) for Rhombohedral andHexagonal R2Fe17 alloys(µ0H = 0 − 5 T)

Heat Capacity and Total Entropy

Temperature dependence of AdiabaticTemperature Change

Heat Capacity and Total Entropy

Temperature dependence of AdiabaticTemperature Change

Magnetovolume Anomalies and Magnetocaloric Effect of R2Fe17compoundsEffect of Ball-Milling

NPD patterns for Bulk and BMPr2Fe17 alloys

SEM images forBM Nd2Fe17 alloys TEM images

for 20h-BMNd2Fe17 alloy

Hystogram for20h-BMNd2Fe17 alloy

SEM images forBM Nd2Fe17 alloys

TEM imagesfor 20h-BMNd2Fe17 alloy

SEM images forBM Nd2Fe17 alloys TEM images

for 20h-BMNd2Fe17 alloy

M vs T for Bulk and 10h-BMPr2Fe17 alloys

∆SM(T ) for Nd2Fe17alloys

RCP values forNd2Fe17 alloys

Outline

4 Conclusions

Magnetocaloric Effect in Pseudobinary AxB2 -xFe17 alloysMagnetic Properties

AxB2 -xFe17 alloys SynthesizedY1.2Ce0.8Fe17 (253 K) - Pr1.5Ce0.5Fe17 (264 K) - Dy1.15Ce0.85Fe17 (273 K) - YPrFe17 (290 K)

XRD Pattern forDy1.15Ce0.85Fe17pseudobinary alloy

M VS T for YPrFe17pseudobinary alloy

MS VS T for AxB2 -xFe17alloys

Rhombohedral Crystal Structure

TC ≈ RT

Magnetocaloric Effect in Pseudobinary AxB2 -xFe17 alloysMagnetocaloric Effect

M(T ,H) curves forCe-based AxB2 -xFe17alloys

∆SM(T ,H) for Ce-basedAxB2 -xFe17 alloys

RCP for AxB2 -xFe17alloys

Magnetocaloric Effect in Pseudobinary AxB2 -xFe17 alloysMagnetocaloric Effect

M(T ,H) curves forCe-based AxB2 -xFe17alloys

∆SM(T ,H) for Ce-basedAxB2 -xFe17 alloys

RCP for AxB2 -xFe17alloys

Magnetocaloric Effect in Pseudobinary AxB2 -xFe17 alloysMaster Curve

Master Curve: Theory

∆SM (T ) → ∆SM (T )/∆SPeakM

θ = (T − TC)/(Tr1 − TC)

{(T − TC)/(Tr1 − TC) T ≤ TC

(T − TC)(Tr2 − TC) T > TC

Master Curve for Ce-based AxB2 -xFe17 alloys

Master Curve for Ce-basedAxB2 -xFe17 alloys

Magnetocaloric Effect in Pseudobinary AxB2 -xFe17 alloysMaster Curve

Master Curve: Theory

∆SM (T ) → ∆SM (T )/∆SPeakM

θ = (T − TC)/(Tr1 − TC)

{(T − TC)/(Tr1 − TC) T ≤ TC

(T − TC)(Tr2 − TC) T > TC

Master Curve for Ce-based AxB2 -xFe17 alloys

Master Curve for Ce-basedAxB2 -xFe17 alloys

Outline

4 Conclusions

Magnetic Properties and Magnetocaloric Effect of Fe-based amorphousalloysMagnetic Properties

FeZrBCu Amorphous Alloys ProducedFe90Zr10 (230 K) - Fe90Zr9B1 (209 K) - Fe91Zr7B2 (240 K) - Fe90Zr8B2 (280 K)

Fe88Zr8B4 (301 K) - Fe86Zr7B6Cu1 (321 K) - Fe87Zr6B6Cu1 (230 K)

M(T ) for the FeZrBCu amorphousribbons

Magnetization Isotherms for theNanoperm alloys

Magnetic Properties and Magnetocaloric Effect of Fe-based amorphousalloysMagnetic Properties

FeZrBCu Amorphous Alloys ProducedFe90Zr10 (230 K) - Fe90Zr9B1 (209 K) - Fe91Zr7B2 (240 K) - Fe90Zr8B2 (280 K)

Fe88Zr8B4 (301 K) - Fe86Zr7B6Cu1 (321 K) - Fe87Zr6B6Cu1 (230 K)

M(T ) for the FeZrBCu amorphousribbons

Magnetization Isotherms for theNanoperm alloys

Magnetic Properties and Magnetocaloric Effect of Fe-based amorphousalloysMagnetocaloric Effect

A general view of ∆SM(T )curves for Nanoperm alloys

RCP1(H) for FeZrBCu amorphousalloys

Metallic Gd (µ0H = 5 T)

RCP1 = 687 Jkg−1

RCP2 = 503 Jkg−1

RCP3 = 402 Jkg−1

Width of the ∆SM(T ) Curves

RCP1(H) for FeZrBCu amorphousalloys

Metallic Gd (µ0H = 5 T)

RCP1 = 687 Jkg−1

RCP2 = 503 Jkg−1

RCP3 = 402 Jkg−1

Width of the ∆SM(T ) Curves

Magnetic Properties and Magnetocaloric Effect of Fe-based amorphousalloysMaster Curve

Master Curve for Fe86Zr7B6Cu1amorphous alloy

Comparation of the MasterCurves for the FeZrBCuamorphous alloys

Magnetic Properties and Magnetocaloric Effect of Fe-based amorphousalloysMaster Curve

Master Curve for Fe86Zr7B6Cu1amorphous alloy

Comparation of the MasterCurves for the FeZrBCuamorphous alloys

Magnetic Properties and Magnetocaloric Effect of Fe-based amorphousalloysComposite Compounds: an Effective way to Improve the RCP Via the ∆SM (T ) Broadening

Past: Low TemperatureMagnetic Composites

T. Hashimoto et al., J. Appl. Phys. 62 (9)(1987) 3873-3878

Recent: RCP Improvement aroundRT by Using Magnetic Composites

R. Caballero-Flores et al., Appl. Phys. Lett. 98 (2011) 102505

Further CommentsRCP Optimization for a Two-PhaseMagnetic Composite

Shape of ∆SM (T )

Weight Fraction of Both Phases

Applied Magnetic Field

The Maximum Refrigeration Efficiency isattained with Constant Magnetic EntropyChange curves.

A.M. Tishin and Y.I. Spichkin. Magnetocaloric Effectand Its Applications. Series in Condensed MatterPhysics, 1 edition (2003).

Shape of ∆SM (T )

Magnetic Properties and Magnetocaloric Effect of Fe-based amorphousalloysA Concrete Two-Phase Composite based on amorphous FeZrCuB ribbons: EXAMPLE 1

∆SM(T ) curves of ComponentA (Fe90Zr9B1) and B (Fe87Zr6B6Cu1)

∆SM(T ) curves of the CompositeSystem 0.4 A + 0.6 B

∆SM (T ) for the two-ribbon system0.5 A (Fe87Zr6B6Cu1) + 0.5 B (Fe90Zr8B2)

Increase of δTFWHM for the Two-Phase System

0.5 A (Fe87Zr6B6Cu1) + 0.5 B (Fe90Zr8B2)

Resulting RCP for the Two-Phase System

0.5 A (Fe87Zr6B6Cu1) + 0.5 B (Fe90Zr8B2)

RCP ≈ 95% of Metallic Gd

0.5 A (Fe87Zr6B6Cu1) + 0.5 B (Fe90Zr8B2)

RCP ≈ 95% of Metallic Gd

0.5 A (Fe87Zr6B6Cu1) + 0.5 B (Fe90Zr8B2)

RCP ≈ 95% of Metallic GdP. Alvarez (University of Oviedo) MCE and magnetovolume effects in Fe-based alloys 04/07/11 43 / 48

Magnetic Properties and Magnetocaloric Effect of Fe-based amorphousalloysFlattening of the ∆SM (T ) Curve

Flattening of ∆SM(T ) for the system0.5 A (Fe87Zr6B6Cu1) + 0.5 B (Fe90Zr8B2)

Magnetic Properties and Magnetocaloric Effect of Fe-based amorphousalloysFlattening of the ∆SM (T ) Curve

Flattening of ∆SM(T ) for the system0.5 A (Fe87Zr6B6Cu1) + 0.5 B (Fe90Zr8B2)

Conclusions

The R2Fe17 alloys cell volume decreases when the temperature is increased in themagnetically oredered state, with a minimum located around TC . The magnetostriction iscorrelated with the total Fe-magnetic moments.

The MCE depends on the magnetic structure:Ferromagnetic→ single-peak magnetic entropy change;Ferrimagnetic→ double-peak with opposite sign;Ce2Fe17 → double-peak with the same sign.

The Curie temperature is largely decreased with pressure ( dTCdP ≈ −10 K/kBar for Tm2Fe17

alloy).

The microstructure is modified by ball-milling without changes in either the magnetic norcrystal structures.Grain breaking (nanosized scale)→ Curie temperature distribution and wider |∆SM |(T )curves.

AxB2 -xFe17 alloys have been synthesized in the rhombohedral phase. The Curietemperatures, RCP and ∆SM are tuned combining different rare-earths.

Temperature of the maximum magnetic entropy change of FeZrBCu amorphous alloys istuned by changes in the %Fe. Spreading of the |∆SM |(T ) curve as wider as 230 K.

Optimizing the selection of both, the δTC of the two Nanoperm alloys which form a two-phasecomposite system and their relative weight fraction→ enhancement of the Relative CoolingPower due to the increase of δTFWHM of the ∆SM and flattening of the ∆SM (T ) curves (up to100 K for µ0∆H = 5 T).

GRACIAS POR VUESTRA ATENCION

Perspectives

Synthesize Y2Fe17 in both rhombohedral and hexagonal crystal structures, andGd2Fe17, Tb2Fe17 and Dy2Fe17 in hexagonal crystal structure.

Y2Fe17, Pr2Fe17 and Nd2Fe17 alloys exhibit the largest magnetic entropy change values→combination of these alloys or synthesis of PrNdFe17 pseudobinaries to optimize the MCEproperties.

Due to the change of the Tm2Fe17 Curie temperature with pressure, and that Tm2Fe17exhibits magnetovolume anomalies, it would exhibit a large magneto-barocaloric effect.

Ball-milling provokes a broadening of the magnetic transitions→ The Tm2Fe17spin-reorientation would not occur over a critical pressure→ Study the MCE when themagnetic anisotropy is along the uniaxial direction.

Measure the temperature dependence of the heat capacity in FeZrBCu alloys to determinethe adiabatic temperature change. Optimize the total entropy of combined two-ribbonssystems to enhance the adiabatic temperature change.

Magnetocaloric and magnetovolume effects in Fe-based alloys

Education

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