Magnetocaloric and magnetovolume effects in Fe-based alloys

Magnetocaloric and magnetovolume effects in Fe-based alloys

Pablo Alvarez Alonso

Department of Material Science and Metallurgic Engineering
University 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 Introduction
Magnetocaloric Effect
Magnetovolume Anomalies
R2 Fe17 alloys
FeZrBCu amorphous alloys


Outline

1 Introduction
R2 Fe17 alloys

2 Experimental Techniques
Fabrication
Structural and Magnetic Characterization


Outline

1 Introduction
R2 Fe17 alloys

Fabrication

3 Results
Magnetovolume Anomalies and Magnetocaloric effect of R2 Fe17 compounds
Magnetocaloric Effect in Pseudobinary Ax B2 -x Fe17 alloys
Magnetic Properties and Magnetocaloric Effect of Fe-based amorphous alloys


Outline

1 Introduction
R2 Fe17 alloys

Fabrication

3 Results

4 Conclusions


Magnetocaloric effect
Origin


Deﬁnition and Theory

Total Entropy of
Metallic Gd under
Two Applied
Magnetic Fields.



Total Entropy of Adiabatic Temperature
Metallic Gd under Change (∆Tadi ) of Gd
Two Applied
Magnetic Fields.



Total Entropy of Adiabatic Temperature Magnetic Entropy
Metallic Gd under Change (∆Tadi ) of Gd Change for GdAl2
Two Applied
Magnetic Fields.



Total Entropy of Adiabatic Temperature Magnetic Entropy
Metallic Gd under Change (∆Tadi ) of Gd Change for GdAl2
Two Applied
Magnetic Fields.

Maxwell Relation
Isothermal Magnetic Entropy Change
H2 ∂M
∆SM (T , H2 )P,∆H = dH
H1 ∂T P,H


Magnetic Refrigeration: Principles and Applications


Magnetic Refrigeration: Principles and Applications

Applications

Consumer Electronics
Air conditioning Active cooling of
Dehumidiﬁers electronic circuits
Refrigerators
Motor refrigerators Medicine
Magnetic resonance
Commercial imaging
Vending machines Portable coolers
Cooling drinks
Cold store Science
Exhibitors & Gas liquefaction
Showcases Cryogenics

Adventages

Low maintenance
Less energy costs
consumption Large durability and
High cooling efﬁciency stability
Environmental friendly No mechanical
vibrations


Relative Cooling Power

Estimation of RCP
Relative Cooling Power RCP1 (H) = |∆SM
Peak
(H) | × δTFWHM
(RCP) RCP2 (H) =
TH
|∆SM (T , H)| dT .
TC

RCP3 (H) = max ∆Smag (T1 , H) × (T2 − T1 )

Peak
Combination of δTFWHM and ∆SM
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

1 Introduction
R2 Fe17 alloys

Fabrication

3 Results

4 Conclusions



Lattice Parameters a and
c, and the cell volume V
vs T for Sm2 Fe14 B



Magnetovolume anomalies: Coupling between
vs T for Sm2 Fe14 B the crystal lattice and the magnetism

Extrapolation from the Non-Ordered
State
Gruneisen relation
¨
κΓCp (T )
αnm (T ) =
3V



Magnetovolume anomalies: Coupling between
vs T for Sm2 Fe14 B the crystal lattice and the magnetism

Extrapolation from the Non-Ordered
State
Gruneisen relation
¨
κΓCp (T )
αnm (T ) =
3V

Magnetostriction

λa = (a − a0 )/a0
λc = (c − c0 )/c0
ωS = (V − V0 )/V0


Outline

1 Introduction
R2 Fe17 alloys

Fabrication

3 Results

4 Conclusions


R2 Fe17 alloys
Crystal Structure

Rhombohedral Th2 Zn17 -type (R3m space group)

Y
Ce
Pr
Nd
Sm
Gd
Tb
Dy


R2 Fe17 alloys
Crystal Structure


Y
Ce
Pr
Nd
Sm
Gd
Tb
Dy

Hexagonal Th2 Ni17 -type (P63 /mmc space group)
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Y


R2 Fe17 alloys
Crystal Structure


Y
Ce
Pr
Nd Fe1(6c): <<Dumm-bell site>>
Sm Oriented along the c-axis
Gd
Tb
Dy

Hexagonal Th2 Ni17 -type (P63 /mmc space group)
Gd
Tb
Dy
Ho Fe1(4f): <<Dumm-bell site>>
Er Oriented along the c-axis
Tm
Yb
Lu
Y


R2 Fe17 alloys
Magnetovolume Anomalies and Magnetocaloric Effect in R2 Fe17 alloys

Magnetovolume Anomalies: Causes
DFe−Fe ˚
2.45 A → Negative exchange Interactions
Dumb-bell sites
˚
DFe−Fe ≥ 2.45 A → Positive exchange Interactions


R2 Fe17 alloys

DFe−Fe ˚
Dumb-bell sites
˚

Magnetovolume Anomalies: Effects
Anomalous thermal expansion
Negative pressure dependence of TC


R2 Fe17 alloys

DFe−Fe ˚
Dumb-bell sites
˚

Magnetovolume Anomalies: Effects
Anomalous thermal expansion
Negative pressure dependence of TC

Magnetocaloric Effect in R2 Fe17 alloys

Magnetic Properties
R2 Fe17 alloys exhibit SOPT
TC arround RT H. Chen et al., JM 3
320 (2008) 1382-1384
Large MS


Outline

1 Introduction
R2 Fe17 alloys

Fabrication

3 Results

4 Conclusions


Fe-content variation of TC for
Nanoperm alloys
∆SM (T ) for Nanoperm alloys

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

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

Magnetic and Magnetocaloric Properties
Broad Second Order Magnetic Phase Transition
Tunnable Curie Temperatures in the RT Regime
Moderate values of MS


Outline

1 Introduction
R2 Fe17 alloys

Fabrication

3 Results

4 Conclusions


Fabrication

Arc Furnace Melt Spinner

Furnace Ball-Mill


Outline

1 Introduction
R2 Fe17 alloys

Fabrication

3 Results

4 Conclusions


Characterization
Structure 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)


Characterization
Magnetic Characterization

VSM PPMS SQUID
University of Sevilla University of Oviedo University of Cantabria
University of Cantabria Slovak Academy of Science
IPICYT


Outline

1 Introduction
R2 Fe17 alloys

Fabrication

3 Results

4 Conclusions


Magnetovolume Anomalies and Magnetocaloric Effect of R2 Fe17
compounds
Crystal and Magnetic Structure

XRPD patterns for NPD pattern below and over
Rhombohedral and TC
Hexagonal R2 Fe17
alloys


compounds

XRPD patterns for NPD pattern below and over
Rhombohedral and TC
Hexagonal R2 Fe17
alloys

Magnetic Structure
Pr2 Fe17 , Nd2 Fe17 and Y2 Fe17 → Collinear Ferromagnetic
Gd2 Fe17 , Tb2 Fe17 , Dy2 Fe17 , Ho2 Fe17 , Er2 Fe17 and Tm2 Fe17 → Collinear Ferrimagnetic
(Tm2 Fe17 Spin Reorientation at 100 K)
Ce2 Fe17 and Lu2 Fe17 → Complex Magnetic Behavior


compounds

XRPD patterns for NPD pattern below and over Ferrimagnetic
Rhombohedral and TC Structure
Hexagonal R2 Fe17
alloys

Magnetic Structure
Pr2 Fe17 , Nd2 Fe17 and Y2 Fe17 → Collinear Ferromagnetic
Gd2 Fe17 , Tb2 Fe17 , Dy2 Fe17 , Ho2 Fe17 , Er2 Fe17 and Tm2 Fe17 → Collinear Ferrimagnetic
(Tm2 Fe17 Spin Reorientation at 100 K)
Ce2 Fe17 and Lu2 Fe17 → Complex Magnetic Behavior


compounds

NPD pattern for the Dy2 Fe17 alloy

Rhombohedral Dy2 Fe17
Ferrimagnetic (TC = 363 K)


compounds

Thermo-Diffraction experiments


compounds

Thermo-Diffraction experiments

Er2 Fe17 Magnetic Moments Tb2 Fe17 Magnetic Moments


compounds

VCell (T ) for Rhombohedral and Hexagonal R2 Fe17 alloys

Extrapolation V(T)


compounds
Linear and Volume Magnetostriction

λa = (a − a0 )/a0
λc = (c − c0 )/c0

ωS = (V − V0 )/V0


compounds
Linear and Volume Magnetostriction

λa = (a − a0 )/a0
λc = (c − c0 )/c0

ωS = (V − V0 )/V0

Comparation between ωS and MFe


compounds
Lattice Parameters a and c
vs Pressure for Dy2 Fe17 and
Er2 Fe17 alloys- RT


compounds
vs Pressure for Dy2 Fe17 and First-Order Birch-Murnaghan
Er2 Fe17 alloys- RT Equation of State

−7/3 −5/3
3 V V
P= B0 −
2 V0 V0

P(V ) curve for the Gd2 Fe17 alloy


compounds
vs Pressure for Dy2 Fe17 and First-Order Birch-Murnaghan
Er2 Fe17 alloys- RT Equation of State

−7/3 −5/3
3 V V
P= B0 −
2 V0 V0

P(V ) curve for the Gd2 Fe17 alloy

V vs T for Er2 Fe17 alloy


compounds

M vs T under Pressure for Pr2 Fe17
compound

dTC
dP
≈ −4 K/kBar


compounds

M vs T under Pressure for Pr2 Fe17 M vs T under Pressure for Tm2 Fe17
compound compound

dTC dTC
dP
≈ −4 K/kBar dP
≈ −10 K/kBar


compounds

M vs (T , H)


compounds

∆SM (T ) for Rhombohedral and
Hexagonal R2 Fe17 alloys
(µ0 H = 0 − 5 T)

M vs (T , H)


compounds

Heat Capacity and Total Entropy


compounds

Temperature dependence of Adiabatic
Temperature Change
Heat Capacity and Total Entropy


compounds
Effect of Ball-Milling

NPD patterns for Bulk and BM
Pr2 Fe17 alloys


compounds SEM images for
BM Nd2 Fe17 alloys
NPD patterns for Bulk and BM
Pr2 Fe17 alloys


compounds SEM images for
BM Nd2 Fe17 alloys TEM images
NPD patterns for Bulk and BM for 20h-BM
Pr2 Fe17 alloys Nd2 Fe17 alloy

Hystogram for
20h-BM
Nd2 Fe17 alloy


compounds

M vs T for Bulk and 10h-BM
Pr2 Fe17 alloys


compounds ∆S (T ) for Nd Fe
M 2 17
alloys

Pr2 Fe17 alloys


compounds ∆S (T ) for Nd Fe
M 2 17
alloys
RCP values for
Nd2 Fe17 alloys

Pr2 Fe17 alloys


Outline

1 Introduction
R2 Fe17 alloys

Fabrication

3 Results

4 Conclusions


Magnetic Properties

Ax B2 -x Fe17 alloys Synthesized
Y1.2 Ce0.8 Fe17 (253 K) - Pr1.5 Ce0.5 Fe17 (264 K) - Dy1.15 Ce0.85 Fe17 (273 K) - YPrFe17 (290 K)

XRD Pattern for M VS T for YPrFe17 MS VS T for Ax B2 -x Fe17
Dy1.15 Ce0.85 Fe17 pseudobinary alloy alloys
pseudobinary alloy

Rhombohedral Crystal Structure
TC ≈ RT



∆SM (T , H) for Ce-based
M(T , H) curves for Ax B2 -x Fe17 alloys
Ce-based Ax B2 -x Fe17
alloys



∆SM (T , H) for Ce-based
M(T , H) curves for Ax B2 -x Fe17 alloys
Ce-based Ax B2 -x Fe17
alloys

RCP for Ax B2 -x Fe17
alloys


Master Curve

Master Curve: Theory
Peak
∆SM (T ) → ∆SM (T )/∆SM

θ = (T − TC )/(Tr1 − TC )

T → (T − TC )/(Tr1 − TC ) T ≤ TC
θ =
(T − TC )(Tr2 − TC ) T > TC


Master Curve for Ce-based Ax B2 -x Fe17 alloys


Master Curve

Master Curve: Theory
∆SM (T ) → ∆SM (T )/∆SM Peak Master Curve for Ce-based
 Ax B2 -x Fe17 alloys
θ = (T − TC )/(Tr1 − TC )

T → (T − TC )/(Tr1 − TC ) T ≤ TC
θ =
(T − TC )(Tr2 − TC ) T > TC


Master Curve for Ce-based Ax B2 -x Fe17 alloys


Outline

1 Introduction
R2 Fe17 alloys

Fabrication

3 Results

4 Conclusions


Magnetic Properties and Magnetocaloric Effect of Fe-based amorphous
alloys
Magnetic Properties

FeZrBCu Amorphous Alloys Produced
Fe90 Zr10 (230 K) - Fe90 Zr9 B1 (209 K) - Fe91 Zr7 B2 (240 K) - Fe90 Zr8 B2 (280 K)

Fe88 Zr8 B4 (301 K) - Fe86 Zr7 B6 Cu1 (321 K) - Fe87 Zr6 B6 Cu1 (230 K)

M(T ) for the FeZrBCu amorphous Magnetization Isotherms for the
ribbons Nanoperm alloys


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


alloys

Metallic Gd (µ0 H = 5 T)
RCP1 = 687 Jkg−1
RCP1 (H) for FeZrBCu amorphous RCP2 = 503 Jkg−1
alloys RCP3 = 402 Jkg−1


alloys

Metallic Gd (µ0 H = 5 T)
RCP1 = 687 Jkg−1
RCP1 (H) for FeZrBCu amorphous RCP2 = 503 Jkg−1
alloys RCP3 = 402 Jkg−1

Width of the ∆SM (T ) Curves


alloys
Master Curve

Master Curve for Fe86 Zr7 B6 Cu1
amorphous alloy


alloys
Master Curve

Master Curve for Fe86 Zr7 B6 Cu1 Comparation of the Master
amorphous alloy Curves for the FeZrBCu
amorphous alloys


alloys
Composite Compounds: an Effective way to Improve the RCP Via the ∆SM (T ) Broadening


alloys
Past: Low Temperature
Magnetic Composites

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


alloys
Past: Low Temperature Recent: RCP Improvement around
Magnetic Composites RT by Using Magnetic Composites

(1987) 3873-3878 R. Caballero-Flores et al., Appl. Phys. Lett. 98 (2011) 102505


alloys
Past: Low Temperature Recent: RCP Improvement around
Magnetic Composites RT by Using Magnetic Composites

(1987) 3873-3878 R. Caballero-Flores et al., Appl. Phys. Lett. 98 (2011) 102505

Further Comments
RCP Optimization for a Two-Phase
Magnetic Composite The Maximum Refrigeration Efﬁciency is
attained with Constant Magnetic Entropy
Shape of ∆SM (T ) Change curves.
δTC
A.M. Tishin and Y.I. Spichkin. Magnetocaloric Effect
Weight Fraction of Both Phases and Its Applications. Series in Condensed Matter
Physics, 1 edition (2003).
Applied Magnetic Field


alloys
A Concrete Two-Phase Composite based on amorphous FeZrCuB ribbons: EXAMPLE 1

∆SM (T ) curves of Component ∆SM (T ) curves of the Composite
A (Fe90 Zr9 B1 ) and B (Fe87 Zr6 B6 Cu1 ) System 0.4 A + 0.6 B


alloys

∆SM (T ) for the two-ribbon system
0.5 A (Fe87 Zr6 B6 Cu1 ) + 0.5 B (Fe90 Zr8 B2 )


alloys
Increase of δTFWHM for the Two-Phase System
0.5 A (Fe87 Zr6 B6 Cu1 ) + 0.5 B (Fe90 Zr8 B2 )

0.5 A (Fe87 Zr6 B6 Cu1 ) + 0.5 B (Fe90 Zr8 B2 )


alloys
Increase of δTFWHM for the Two-Phase System
0.5 A (Fe87 Zr6 B6 Cu1 ) + 0.5 B (Fe90 Zr8 B2 )

0.5 A (Fe87 Zr6 B6 Cu1 ) + 0.5 B (Fe90 Zr8 B2 )

Resulting RCP for the Two-Phase System
0.5 A (Fe87 Zr6 B6 Cu1 ) + 0.5 B (Fe90 Zr8 B2 )

RCP ≈ 95% of Metallic Gd

alloys
Flattening of the ∆SM (T ) Curve

Flattening of ∆SM (T ) for the system
0.5 A (Fe87 Zr6 B6 Cu1 ) + 0.5 B (Fe90 Zr8 B2 )


Conclusions
The R2 Fe17 alloys cell volume decreases when the temperature is increased in the
magnetically oredered state, with a minimum located around TC . The magnetostriction is
correlated 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;
Ce2 Fe17 → double-peak with the same sign.
dTC
The Curie temperature is largely decreased with pressure ( dP
≈ −10 K/kBar for Tm2 Fe17
alloy).
The microstructure is modiﬁed by ball-milling without changes in either the magnetic nor
crystal structures.
Grain breaking (nanosized scale) → Curie temperature distribution and wider |∆SM |(T )
curves.
Ax B2 -x Fe17 alloys have been synthesized in the rhombohedral phase. The Curie
temperatures, RCP and ∆SM are tuned combining different rare-earths.
Temperature of the maximum magnetic entropy change of FeZrBCu amorphous alloys is
tuned 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-phase
composite system and their relative weight fraction → enhancement of the Relative Cooling
Power due to the increase of δTFWHM of the ∆SM and ﬂattening of the ∆SM (T ) curves (up to
100 K for µ0 ∆H = 5 T).


´
GRACIAS POR VUESTRA ATENCION


Perspectives

Synthesize Y2 Fe17 in both rhombohedral and hexagonal crystal structures, and
Gd2 Fe17 , Tb2 Fe17 and Dy2 Fe17 in hexagonal crystal structure.
Y2 Fe17 , Pr2 Fe17 and Nd2 Fe17 alloys exhibit the largest magnetic entropy change values →
combination of these alloys or synthesis of PrNdFe17 pseudobinaries to optimize the MCE
properties.
Due to the change of the Tm2 Fe17 Curie temperature with pressure, and that Tm2 Fe17
exhibits magnetovolume anomalies, it would exhibit a large magneto-barocaloric effect.
Ball-milling provokes a broadening of the magnetic transitions → The Tm2 Fe17
spin-reorientation would not occur over a critical pressure → Study the MCE when the
magnetic anisotropy is along the uniaxial direction.
Measure the temperature dependence of the heat capacity in FeZrBCu alloys to determine
the adiabatic temperature change. Optimize the total entropy of combined two-ribbons
systems to enhance the adiabatic temperature change.


Magnetocaloric and magnetovolume effects in Fe-based alloys

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Magnetocaloric and magnetovolume effects in Fe-based alloys