Multiferroic Thin Multiferroic Thin FilmsFilms

Nanoscience Symposium Nanoscience Symposium 20062006

June 15June 15

By: Arramel

RuG

ContentsContents1.1. Introduction.Introduction.2.2. The ME Effects.The ME Effects.3.3. Fascinating of Multiferroics.Fascinating of Multiferroics.4.4. Mechanisms of Multiferroicity.Mechanisms of Multiferroicity.5.5. Multiferroic Thin Films.Multiferroic Thin Films.6.6. Conclusion.Conclusion.

Hysterisis Hysterisis LoopLoop

Temperature Temperature DependenceDependence

Ferromagnetism. Display spontaneous

magnetization. Produce Hysterisis Loop. Can be found mainly in metals.

Ferroelectricity. Display spontaneous

polarization. Produce Hysterisis Loop. Ferroelectrics are insulators

H, E

The Linear ME EffectsThe Linear ME Effects Induced coupling of Magnetic and Electric properties.Induced coupling of Magnetic and Electric properties. Expansion of free energy of a material.Expansion of free energy of a material.

jiijiSii

Si EEHMEPFHEF 00 2

1),(

More clearly:More clearly:

jjiiij 2i

i EFP

i

i HFM

NoteNote::

...21

0 jiijjiij HEHH

ME Signal ME Signal MeasurementsMeasurements

H = 0 H ≠ 0

Fascinating of Fascinating of MultiferroicsMultiferroics

A material that simultaneously exhibits ferromagnetism A material that simultaneously exhibits ferromagnetism and ferroelectricity.and ferroelectricity.

These materials show the largest ME Effects.These materials show the largest ME Effects. Application such as: novel multi-state storage device.Application such as: novel multi-state storage device.

Pacific Custom Cable. Inc Nur. H, et.al, Nature 429, 2004

LimitationsLimitations Hard to be found in nature & difficult to produce by synthetic routes. Ferromagnets and Ferroelectrics are excluded each other.

“Non standard” Ferromagnets (which is not metallic) or “Non standard” Ferroelectrics (not driven by d0 cation).

PossibilitiesPossibilities

For example:Perovskite BiFeO3

Mechanisms of Mechanisms of MultiferroicityMultiferroicity1. Non-standard Ferroelectrics.1. Non-standard Ferroelectrics.

Lone-pair asymmetry. Lone-pair asymmetry. Electrostatic and size effects.Electrostatic and size effects.

2. Insulating magnets. ME Effects in inhomogeneous Antiferromagnetic materials. Spiral Magnets.

Van Aken, et.al, Nature Material, 3, 164 (2004). Kimura, T et.al, Phys. Rev. B 68, 060403(R) (2003).

Ferroelectricity inFerroelectricity in TbMnOTbMnO3 3

Kimura T, et.al, Nature 426, 55 (2003).

Existence of the Existence of the CouplingsCouplings

Kimura, et.al, Physical Review B 71, 224425 (2005)Fiebig M, J. Phys. D: Appl. Phys. 38.123 (2005).

(RE)MnO(RE)MnO33 vs Other vs Other MultiferroicsMultiferroics

REMnREMn FE TFE TCC TTNéelNéel

TbMnOTbMnO33 27 K27 K 41 K41 K

GdMnOGdMnO33 23 K23 K 43 K43 KDyMnODyMnO33 18 K18 K 39 K39 K

OtherOther FE TFE TCC TTNéelNéel

BiFeOBiFeO33 1083 K1083 K 653 K *653 K *BiMnOBiMnO

33750 K750 K FM TFM TCC = =

105 K *105 K *YMnOYMnO33 900 K900 K 70 K **70 K **

Temperature gap is too wide.The above oxides only existed on low temperatures.

* Prellier. W, et.al, J. Phys.: Condens. Matter , 17, R803 (2005)

** Van Aken, et.al, Nature Material, 3, 164 (2004).

Spiral MagnetsSpiral Magnets

Expression of Spin Density Wave (SDW)Expression of Spin Density Wave (SDW)

Mostovoy. M, Physical Review Letter 96, 067601 (2006).

.Q x P1P 3213 eMMxd

V e

Phenomenological Approach

332211 x.Qsinx . Qcos M eMeMeM

Thin Films Thin Films Miniaturization: spintronic, storage, Miniaturization: spintronic, storage,

sensor.sensor. Offers controlled way to synthesize a Offers controlled way to synthesize a

Multiferroic materials.Multiferroic materials. Enhancement of ME couplings is Enhancement of ME couplings is

possible.possible.

Growth of Complex oxides with Atomic Layer ControlGrowth of Complex oxides with Atomic Layer Control

Pulsed Laser Deposition & in-situ Pulsed Laser Deposition & in-situ Reflective High Energy Electron Reflective High Energy Electron

DiffractionDiffraction

BiFeOBiFeO33 Thin Film Thin Film

Wang. J, Science, 299, 1719 (2003).

BiMnOBiMnO33 Thin Film Thin Film

Eerenstein , W. Applied Physics Letters, 87, 101906 (2005) Bog G. Kim, et,al. J.of the Korean Physical Society, 46 (2005).

BiCrOBiCrO33 Thin Film Thin Film

Murakami, et.al, Applied Phy Lett 88, 152902 (2006)

ConclusionConclusion AntiferromagneticAntiferromagnetic RMnORMnO33 have shown large ME have shown large ME couplings couplings

at LT.at LT. Thin films exhibit a large spontaneous polarization Thin films exhibit a large spontaneous polarization

compared to bulk.compared to bulk. In thin films the orientation can be controlled. This is a In thin films the orientation can be controlled. This is a

very very important factor in order to increase their spontaneous important factor in order to increase their spontaneous polarization. polarization.

Thin films of Manganites are promising as multiferroic Thin films of Manganites are promising as multiferroic materials withmaterials withM≠0, P=0 at room temperature, which will have enourmous M≠0, P=0 at room temperature, which will have enourmous impact inimpact inmany applications.many applications.

AcknowledgementsAcknowledgements

Thanks to Beatriz NohedaThanks to Beatriz Noheda

FerromagnetismFerromagnetism

Hill, N, J. Phys. Chem. B 2000, 104, 6694-6709

YMnOYMnO3 3 Thin Film Thin Film The evidence of The evidence of

ferroelectric ferroelectric materials.materials.

Two form: Epitaxial Two form: Epitaxial & polycristalline.& polycristalline.

Prellier. W, et.al, J. Phys.: Condens. Matter , 17, R803 (2005)

Utilizes a layered structure of Utilizes a layered structure of thin filmsthin films of of magnetic materials.magnetic materials.

One of the One of the ferromagneticferromagnetic layers is layers is "pinned" so its magnetization direction "pinned" so its magnetization direction remains fixed and the other ferromagnetic remains fixed and the other ferromagnetic layer is "free" to rotate with the layer is "free" to rotate with the application of a magnetic field.application of a magnetic field.

Changes its electrical resistance Changes its electrical resistance depending on the direction of an applied depending on the direction of an applied magnetic field.magnetic field.

Spin ValveSpin Valve

Symmetry ArgumentsSymmetry Arguments

Short ExplanationShort Explanation