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Investigation of transport behavior of electron doped dependent manganite

Investigation of transport behavior of electron doped dependent Manganite

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Submitted by

Shreya Ved (91700221007)

Swati Zankat (91700221002)

Ritu Ambasana (91600221029)

Nirali Rajapara (91700221003)

Guided by

Dr. Mukesh J. Keshvani

A Thesis Submitted to

Marwadi University in Partial Fulfillment of the M.Sc. in Physics

May 2018

[image: ]

MARWADI UNIVERSITY

Rajkot-Morbi Road, At & Po. Gauridad”,

Rajkot-360003, Gujarat, India.

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CERTIFICATE

This is to certify that project work embodied in this dissertation titled “ Thickness dependent study of Manganite based materials [image: ]was carried out by Shreya Ved, Swati Zankat, Ritu Ambasana Nirali Rajapara at Marwadi University, Rajkot for partial fulfillment of Master of Science in Physics to be awarded by Marwadi University. This project work has been carried out under my guidance and supervision and it is up to my satisfaction

.

Date :

Place :

Dr. Mukesh J. Keshvani

Dr. Jenishkumar Patel

Dr. Vaibhav Maheta

Assistant Professor”,

Head of the Department”,

Principal”,

Department of Physics”,

Department of Physics”,

Faculty of Science”,

Marwadi University, Rajkot

Marwadi University, Rajkot

Marwadi University, Rajkot

Seal of Institute

i

[bookmark: page3]COMPLIANCE CERTIFICATE

This is to certify that project work embodied in this dissertation titled “Thickness dependent study of manganite based material ” was carried out by Shreya Ved (91700221007)Swati Zankat (91700221002) Ritu Ambasana (91600221029)Nirali Rajapara (91700221003)[image: ]at Marwadi University for partial fulfillment of Master of Science in Physics to be awarded by Marwadi University. They has complied to the comments given during Review I, Review II, Review III, Review IV, by Reviewer to my satisfaction.

Date :

Place :

Shreya Ved (91700221007)

Dr. Mukesh J. Keshvani

Assistant professor

Swati Zankat (91700221002)

Department of Physics

Marwadi University, Rajkot

Ritu Ambasana (916002210229)

Nirali Rajapara (91700221003)

II

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PROJECT APPROVAL CERTIFICATE

This is to certify that research/project work embodied in this dissertation titled “ Thicknness dependent study of Manganite based materials ” was carried out by Shreya Ved (91700221007)”,

[image: ]

Swati Zankat (91700221002), Ritu Ambasana (91600221029) and Nirali Rajapara (91700221003) at Marwadi University is approved for the Master of Science in Physics by Marwadi University.

Date :

Place :

Examiner’s Sign and Name:

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)

iii

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DECLARATION OF ORIGINALITY PAGE

We hereby certify that we are the sole authors of this project work and that neither any part of this thesis nor the whole of the thesis has been submitted for a degree to any other University or Institution.

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We certify that, to the best of our knowledge, the current project work does not infringe upon anyone’s copyright nor violate any proprietary rights and that any ideas, techniques, quotations or any other material from the work of other people included in our project work, published or otherwise, are fully acknowledged in accordance with the standard referencing practices. Furthermore, to the extent that we have included copyrighted material that surpasses the boundary of fair dealing within the meaning of the Indian Copyright (Amendment) Act 2012, we certify that we have obtained a written permission from the copyright owner(s) to include such material(s) in the current thesis and have included copies of such copyright clearances to our appendix.

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We declare that this is a true copy of project work, including any final revisions, as approved by project work review committee.

We have checked write up of the present project work using anti-plagiarism database and it is in allowable limit. Even though later on in case of any complaint pertaining of plagiarism, we are sole responsible for the same and we understand that as per UGC norms, University can even revoke Degree name conferred to the student submitting this thesis.

Date:

Place:

Shreya Ved

Ritu Ambasana

Dr. Mukesh J. Keshvani

(91700221007)

(91600221029)

Assistant professor

Department of Physics

Marwadi University

Swati Zankat

Nirali Rajapara

(91700221002)

(91700221003)

iv

[bookmark: page6]Acknowledgement:

This project requires a lot of guidance and appreciation from many people and I am extremely glad to have got this all along the completion of my project. All that I have done is because of their guidance so I would not forget to thank them.

I respect and thank Dr. Mukesh Keshvani assistant professor, Department of physics, Marwadi University, Rajkot for his guidance and gave opportunity to do project work.

With his all support and guidance valuable suggestion, constant encouragement and active supervision it was not possible for us to work on project.

Thanks to our former Principal Dr. Amarpreet Singh Arora, present Principal Dr. Vaibhav Mehta and also our head of department Dr. Jenishkumar Patel for providing all support.

We are extremely thankful to department of physics, department of microbiology and department of chemistry for allowing us to use their all facilities during project work.

Special thanks to Marwadi university for providing financial support .We are hearty thankful to Dr. Piyush Solanki and Mr. Keval Gadani for guiding us and for allowing us for using their instrument facility XRD.

World is not enough for expressing thanks to our family and friends who has constantly encouraged us during this months.

Shreya Ved

Swati Zankat

Ritu Ambasana

Nirali Rajapara

I

[bookmark: page7]Abstract:

Table of Contents

1. History

2. Introduction

Mixed valent perovskite manganites

3. Properties and Mechanism

· Magnetic Reversal

· Magnetoresistance

· Zener Double Exchange

· Jahn Teller Distortion

4. Experimental Details

Doping

· Ultrasonication process

· Magnetic Stirring

· Spin Coating

· Muffle Furnance

5. Analysis

· X-ray diffraction

· Four Probe

· SEM-TEM

· Energy Dispersive X-ray Spectroscopy (EDAX)

· LCR / C-T

6. Results and discussions

Refrences

Introduction to Mixed Valent Perovskite Manganites

The Perovskite Crystal is an organometallic halide compound. The mineral was discovered in the Ural Mountains of Russia by Gustav Rose in 1839. It is named after Russian Mineralogist L.A Perovski in1792 [1] It is believed to be the most abundant mineral within the Earth. Victor Goldschmidt first described the perovskite crystal structure in 1926, in his work on tolerance factors which may be us.ed to predict their structures and stability. [2] The synthesis and crystal growth of Perovskite was confronted by Weber around 40 years ago [3-4]. The first metal halide perovskite was deposited through spin coating onto the glass substrate or Quartz at room temperature [5]. The mixed valent perovskite manganites can be expressed as R1-xAxMnO3 where R = Rare Earth Element (Ce, Gd, Nd, La) and A= (Ca, Sr, Pb) are contemplated since 1950. Until the early 1990’s the papers detailing to Perovskite manganites were published [6-7] when CMR was exposed. The Mixed Valence Manganite Oxide R1-xAxMNO3 with three dimensional Perovskite was discovered in 1993.An apprised exertion was carried out by Volger [8], Wollan and Koehler [9] and later on by R.Von Helmholt et al [10] and Jin et al [11]

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In 1994 it was uncovered that Magneto resistance exceeds 99.92% [12″,13] by MC Coromack, Jin, and others. The Manganite material shows CMR~ 99% and thus can be utilized as Bolometers, Magnetic field Sensors; magneto resistive read heads and magnetic memory device.

Perovskite Manganite

An organic-inorganic Perovskite materials exhibits variation in structure, elemental composition as well as the performances. Perovskite is an eye-catching material due to swift raise of 3.8% [14] to 22.1% [15] efficiency in solar cell. An ideal Perovskites are insulating by nature due to the potent bonding of electrons. The mixed valent A1-xBxMnO3 in which A and B are rare earth element. They incur chief concern due to their peculiar magnetic properties [16″,17]. AMnO3 is a trivalent Parent compound which is Antiferromagnetic Insulator but by executing doping of divalent ion it befits to attain Ferromagnetic behavior. The phenomenon such as Zener double exchange, electron –phonon interaction due to Jahn-Teller effect to explicate magneto resistance in double exchange model [18] are extensively remarked. They exhibit electronic and magnetic transition above room temperature and optimum CMR effect is seen only under high magnetic field ~8-9 Tesla. Additionally a noticing characteristic of metallic Manganese oxide is being completely polarized i.e. orientation of mobile electrons in single direction.

Magneto resistance

The phenomenon of Magneto Resistance was inaugurated by W.Thomson (Lord Kelvin) [19]. The value of MR can be equated by formula:

MR%=

ρ(H) =Resistivity of applied field at a given temperature

ρ(0) = Resistivity under zero magnetic field

The value of MR can be possibly positive or negative depending upon the increment or decrement in resistivity. CMR is an attribution of manganites based Perovskite oxide that activates to orient the alternation in their electrical resistance in the vicinity of magnetic field by several orders in terms of magnitude. An essence of CMR is illustrated due to strong bonding of spin, charge and lattice degree of freedom. MR arises due to interaction of magnetic properties and electron transport. Initially the sample is Paramagnetic by nature but by employing magnetic field the Paramagnetic nature change over to Ferromagnetic due to the alignment of spin which is eventually responsible for the transport of Mn ions. It was specifically reported by Jin et al that at 77K temperature under the application of magnetic field around 6T, maximum CMR i.e. ~100.00% is attained for Calcium doped Manganese Oxide [20]. In case of Metals, the reported value of MR is only few percentage even in the presence of higher magnetic field. Volger explosed the MR on manganites and noted that in presence of magnetic field the resistivity of material decreases when they are obessed with ferromagnetic behavior [21].When MR exceeds in magnitude than previously noted values it is termed as GMR [22]. When the observed variation was comparatively larger the name CMR was coined to differentiate it from GMR.

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Zener Double Exchange

In mixed valent manganites two Mn ions are responsible for the conduction phenomenon which was put forwarded by C. Zener [23″,24] and is therefore named as Zener double exchange [25″,26]. Under an influence of this mechanism an insulating paramagnetic behavior transits to metallic ferromagnetic state. This model is relatively similar to super exchange where alignment of Ferromagnetic and Antiferromagnetic state takes place between two atoms whereas in double exchange interaction is possible when one atom has excess electron compared to the other[27″,28]. Due to the presence of potential difference Mn+3 hops to Mn+4 which is possible due to the presence of oxygen which acts as a ligand ion forming a complex coordination. In the outermost orbital of oxygen two electrons exists having up and down spins consequently. But according to Hund’s rule two electrons with an identical spin cannot coexist in single orbital. The Mn+3 will donate it’s eg electron to oxygen which will later be donated to vacant eg orbitals of Mn+4 by the oxygen atom. The Zener double exchange mechanism is feasible only when the spins of adjacent Mn+ are in parallel orientation where observed hopping between the ions is supposed to be extreme under low temperature. Any misalignment, disorder or raise in the temperature will lead to such a resulting spin which will probably reduce Zener mechanism. The resistivity is extended when temperature is increased and eventually leads to interruption in alignment of spin. In order to achieve exact spin alignment, magnetic field is applied resulting in reduction of resistivity. The maximum variation in resistivity is noted near Tc value due to the application of external field.

[image: https://upload.wikimedia.org/wikipedia/commons/d/da/Double-exchange.PNG]

Jahn-Teller distortion

Any rare earth element such as LaMnO3, PrMnO3, and NdMnO3 are remarked to be an insulator without doping at all possessed temperature. The Mno3 orbitals are affected by crystal field due to which it results into a pair of degenerate orbitals namely eg (a doublet) and t2g (a triplet). The oxygen ions have an ability to alter their positions generating asymmetry and are also creditworthy to eliminate the degeneracy. The deformation in the energy levels will lead to reduction in symmetry and eventually to Jahn-Teller distortion. To suppress the action of Jahn-Teller distortion Mn+4 content must be high. There are 21 modes of vibration possibly occurring in manganites responsible for the motion of Mn and O ions. [29]

Tolerance factor

It is a measure for stability and distortion of crystal structure. It was descripted by Goldschmidt in 1926. It is a dimensionless number and is calculated from the ratio of ionic radii.

t =

rA- radius of A cation

rB- radius of B cation

rO- radius of anion (oxygen)

t =

It is an indication for the stability is the distance between A site cation to nearest oxygen ion and is the distance between B site anion to the nearest ion. To attain undistorted cubic structure Mn-O-Mn link will be found straight. When t=1 in case of cubic structure for t

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