# Presentation: 014176

## Soft x-ray resonant scattering in manganites:

***from bulk crystals to thin films***

**Jessica Thomas**
**Physics Department, Brookhaven National Lab**

## Outline

**I:  Probing orbital and spin correlations in half-doped manganites with SXRD**
**—****  ****Why are we interested in orbital physics?**
**—****  ****Advantage of tuning to the Mn L-edge (~650 eV) **
**—**** ****	**** ****Experimental results and modeling the ground state**
**     ****in a half-doped manganite**
**—****  ****Future projects**
**II: Ferroelectrically doped manganite thin films**
**—****  ****X-ray magnetic resonant scattering studies**
**—****  ****Projects on the horizon**

**Outline**

## eg

**Why study “orbitals”?**

**Active degree of freedom in manganites and correlated electron materials **
**	****	****—**** ****How do orbital correlations drive magnetism (or vice versa)?**
**               — ****Role in magneto-resistance?  **

- Mn 3*d* levels

*3x**2** – r**2*/*3y**2** – r**2*

*y**2** – z**2*/*x**2** – z**2*

- eg

- t2g

**O****2-**

**Mn****3+**

## T

- Goodenough (1955)

- Mn3+

- Mn4+

**Fundamental questions**
** ****To what extent is the ground**
**  ****state charge ordered?**
** ****What drives charge/orbital    **
**  ****order?**
**- Coupling between orbital and   **
**  ****magnetic correlations?**

- PI

- AFI

- FMI

- antiferromagnetic
- insulator

- charge/orbital order

- 0.1

- 0.3

- 0.5

- 0.7

- 0

**x**

**T****OO****/T****CO  ****(240 K)**

**T****N ****(170 k)**

- Pr0.6Ca0.4MnO3

- Magnetic susceptibility

## How do you “see” orbital order with x-ray diffraction?

**How do you “see” orbital order with x-ray diffraction?**

**Resonant diffraction at a Mn aborption edge **

***k****i*

**E = **E**ε**

***k****f*

**Q**

- C. W. M. Castleton and M. Altarelli
- Phys. Rev. B **62** 1033 (2000).

- S. Grenier *et al.* Phys. Rev. B **69** 134419 (2004).

## Magnetic and orbital resonant line shapes:  NSLS X1B 

- weight between the
- magnetic and orbital spectra

***J. Thomas, J. Hill, S. Grenier, P. Abbamonte, M. v. Veenendaal, G. Sawatzky et al. ***
***PRL 92, 237204 (2004)***

**Magnetic and orbital resonant line shapes:  NSLS X1B **

- Orbital scattering
- (x 100)

- Magnetic scattering

**T****N**

**T****OO**
** ****(x 100)**

**Diffracted intensity at Q = (****1⁄2****,0,0)/(0,****1⁄2****,0)**

## Orbital correlations are shorter ranged than magnetic correlations

**Orbital correlations are shorter ranged than magnetic correlations**

- E = 645 eV

- ξorb ~ 370 Å
- ξmag _>_ 720 Å

- Orbital
- Magnetic

## Calculated spectra

- Magnetic spectrum (T < TN)

- Orbital spectrum
- (TN < T < TOO)

- total

- Mn4+

- Mn3+

**Relaxed charge-order model**

## Calculated spectra

- Magnetic spectrum (T < TN)

- Orbital spectrum
- (TN < T < TOO)

- total

- Mn4+

- Mn3+

**Relaxed charge-order model**

## Calculated spectra

- Magnetic spectrum (T < TN)

- Orbital spectrum
- (TN < T < TOO)

- total

- Mn4+

- Mn3+

**Relaxed charge-order model**

-   -   3 eV spectral weight shift
-       between orbital and magnetic
-       resonant diffraction spectra
-   -   Difference in intensity

## PCMO (x=0.4 and 0.5)

**PCMO (x=0.4 and 0.5)**

## Characteristic orbital scattering in half-doped manganites

**Energy (eV)**

**Pr****0.6****Ca****0.4****MnO ****3**

**Pr****0.5****Ca****0.5****MnO ****3**

**Nd****0.5****Sr****0.5****MnO ****3**

## Nd0.5Sr0.5MnO3

- Nanoscale structural correlations in a half doped manganite

- T

- Nd0.5Sr0.5MnO3

- CE AF/
- orbital
- order

- nanoscale
- structural correlations
- (orbital/spin order?)

- FM

**T**

## Summary

**Summary**

**Soft x-ray resonant diffraction in manganites**
** ****Direct probe of magnetic and orbital correlations**
**  ****reveals shorter ranged orbital than magnetic order**
** ****Spectroscopy of 3*****d***** states + calculations:  **
**  ****test of ground state models **

**Importance of orbital correlations in other materials?**
**- Orbital liquids**
**- Role in frustrated spin systems**

## II

**II**
**	****Ferroelectric doping of manganite thin films**

## Ferroelectric doping of ferromagnetic manganite films

**Ferroelectric doping of ferromagnetic manganite films**

- X. Hong *et al* Phys. Rev. B** 68 **(2003)

**(Collaboration with Charles Ahn, Yale University)**

**La****1-x****Sr****x****MnO****3**

## Preliminary questions

- How does the ferroelectric doping modulate the magnetism?
- To what extent does the doping penetrate the LSMO film?
- Comparison between structural and magnetic roughness.
- Mechanism for Tc shift?
- How do magnetic correlations in the manganite
- evolve with PZT geometry and spacing?

## IntensityMCD ~ MFM

- Magnetic Circular Dichroism (MCD) at the Mn LII,III-edges

**Right CPL**

**Left CPL**

- MCD measured in reflectivity mode:  Wiggler beamline X13-A NSLS

**22 Hz flipping of photon polarization**

- Lock-in technique
- separates sum and difference (MCD)

**k****i**

**k****f**

**Intensity****MCD**** ~ M****FM**

**M**

## MCD detection of ferromagnetism in bare 3 nm LSMO films

- MCD detection of ferromagnetism in **bare** 3 nm LSMO films

- MCD signal

**Near Tc**

**LSMO**

**PZT**

**V**

*decreasing*
*T*

## Looking into the future:  manipulating magnetic inhomogeneity

**T**

**La****1-x****Ca****x****MnO****3****:  x ~ 0.5**

**SrTiO****3**

**PZT**

**- Effects of “doping” on formation of the ferromagnetic phase (MCD)**
**- Correlations between the doped regions (Diffraction)**

## Suggestions for development of soft x-ray end-station

**   ****Electronic feed-thrus**
**   ****Azimuthal degree of freedom (rotation of sample about Q)**
**   ****Polarization analysis (at the detector)**
**   ****Calibration method**
**   ****Linear and circularly polarized light**
**   ****Dialogue/development of analytical tools to understand the spectra**

**Suggestions for development of soft x-ray end-station**

## John Hill Physics. Dept, Brookhaven National Laboratory

- John Hill *Physics. Dept, Brookhaven National Laboratory*
- Stephane Grenier *Physics. Dept, Brookhaven National Laboratory*
- Peter Abbamonte *NSLS, Brookhaven National Laboratory*
- Andrivo Rusydi *NSLS, Brookhaven National Laboratory*
- Young-June Kim *Physics. Dept, Brookhaven National Laboratory*
- Y. Tokura  *University of Tokyo, Japan*
- Y. Tomioka *AIST, Japan*
- Des McMorrow *University College, London*
- Michel van Veenendaal *N. Illinois Univ./Argonne National Lab*
- George Sawatzky *University of British Colombia*
- Charles Ahn* Yale University*
- Xia Hong* Yale University*

**Collaborators**

## Transverse scans:  

**Transverse scans**

**645 eV**

**orbital**

**magnetic**

- Transverse scans:
- Orbital correlations are shorter ranged than magnetic correlations

## Orbital/spin order in x > 0.5 manganites

**Wigner crystal vs. bi-stripe structure**