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1$#

Specific heat and Thermodynamics of Titanate Perovskite

Materials

en0 hoithrani N. 3. a0r

5epart,ent o+ Physics* 6arat0llah 8niversity* 6hopal-4%2$2%* India/-,ail ren0choithrani:g,ail.co,

Abstract

Speci+ic heat and ther,odyna,ical properties o+ the ;aTi(&2 have ?een investigated +or the +irst ti,e 0singe@tended rigid ion ,odel !/I". Bith the increase o+ no,inal hole doping =* the syste, 0ndergoes a phasechange +ro, an ins0lating phase to a ,etallic phase at =c

IC $.$# and the low-te,perat0re anti+erro,agnetic phasedisappears at =c

,agC $.$'. ;aTi(&2has ?een s0ggested to have pro,ising scienti+ic and technological applications.(0r co,p0ted speci+ic heat res0lts +ollow the sa,e trends o+ variation with corresponding e@peri,ental data. Theval0es o+ speci+ic heats also increase with te,perat0re. The theoretically co,p0ted ther,odyna,ical properties o+;aTi(&2co,po0nd are in good agree,ent with the availa?le e@peri,ental res0lts.Keywords:Ther,odyna,ical properties* Perovsites* Speci+ic heat* 5e?ye te,perat0re* ohesive energy

1 Introduction

ecently ,etal-ins0lator transitions !IT" in &d-transition ,etal ternary o@ide syste,s have ?een intensivelyinvestigated in order to clari+y the ano,alo0s properties o+ correlated electrons1. (ne o+ the ,ost prototypicalsyste,s is the perovsite-type one* +ro, the ,ineral perovsite ;aTi(&. The per+ect perovsite str0ct0re is ane@tre,ely si,ple one with the che,ical +or,0la A6(&* where A is a ,onovalent* divalent or trivalent alaline- orrare-earth ele,ent and 6 is a pentavalent* tetravalent or trivalent transition-,etal ele,ent s0ch as Ti or n. (ne o+the advantages in st0dying this partic0lar class o+ titanate lies in its relatively si,ple electronic and lattice +eat0resDna,ely* in a stoichio,etric co,po0nd ;aTi(&a relevant electron is only single &d electron per each Ti site*whosenetwor +or,s a si,ple* appro@i,ately c0?ic* lattice1-&. These ,aterials are at the +oc0s o+ scienti+ic research d0e totheir potential technological applications4. (r?ital degrees o+ +reedo,* in addition to spin* charge* and latticestr0ct0re* are gaining increasing interest in c0rrent solid-state physics. That is* in ,anganites the E0estion o+ or?italorder plays a ey role in the 0nderstanding o+ electronic properties s0ch as the colossal ,agnetoresistant e++ect. In

the orthorho,?ic perovsite ;an(&!n&

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Advances in Physics Theories and Applications www.iiste.org

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)ol.19* 2$1& - Selected +ro, International on+erence on ecent Trends in Applied Sciences with /ngineering Applications

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Ta?le1- odel Para,eters and Ther,odyna,ic Para,eters o+ ;aTi(&2odel Para,eters Ther,odyna,ic Para,eters

= Ti-(Y1 !Z"

Ti-(?1!1$-12erg"

;a-(Y2 !Z"

;a-(?2!1$-12erg" !e)"

V$!TFK"

[5!3"

\

$.$1 $.#7$1 $.997' $.7&7% $.%47$ -142.71 1$.4#9 #$1.7%1 2.'9$.$4 $.##9' $.9'%1 $.719' $.%&17 -142.$9 1$.4&' #$$.7#2 2.'#$.$% $.#&79 $.9%14 $.712# $.%2$# -141.9% 1$.4&& #$$.#14 2.'1$.$' $.#14% $.92&7 $.7$19 $.%19' -141.79 1$.427 #$$.21$ 2.7'$.1% $.#2%2 $.942# $.7$72 $.%2$1 -141.'7

!141.'1"1#1$.4&$!1$.7%4"1%

#$$.&%2!#1%.%"1%

2.'$!2-&"17

Jig. 1 The variations o+ speci+ic heat with te,perat0re +or ;aTi(&2* where the solid lines and lines with circles arethe present ,odel calc0lation and e@peri,ental data2* respectively.

' (onclusions

The syste,atic trend o+ variations o+ ther,odyna,ic properties and the closer agree,ent with the availa?lee@peri,ental data on speci+ic heats reveal the s0ita?ility and appropriateness o+ /I +or the ;aTi(&2 ,aterials.So,e o+ the res0lts are* pro?a?ly* ?eing reported +or the +irst ti,e and hence o0r co,,ent on their relia?ility arerestricted 0ntil the report o+ e@peri,ental data on the,. Presently* these val0es are o+ acade,ic interest and they canserve as g0ide to the e@peri,ental worers in +0t0re.

It ,ay ?e concl0ded that /I is e++ectively 0se+0l ,odel +or the 0ni+ied and co,prehensive st0dy o+ theperovsite ,aterials* ?eca0se the ?ea0ty o+ o0r potential lies in satis+actory e@planation o+ the variety o+ physicalproperties !s0ch as cohesive* ther,al* elastic* ther,odyna,ic" with sa,e s0ccess9-11+or the ,0lti+erroics* ,anganitesand other perovsite ,aterials.

Acknowled#ementen0 hoithrani wo0ld lie to acnowledge with thans the Science and /ngineering esearch 6oard*5epart,ent o+ Science and Technology !5ST"* overn,ent o+ India* New 5elhi +or providing the +inancialassistance and the Jast Trac Ho0ng Scientist Award.

%eferences

1. eorges A* 3otliar * 3ra0th B oKen?erg G*Rev Mod Phys,%' !199%" 1&.2. Tag0chi H* (0da T To0ra H*Phys Rev B,#9 !1999" 12.&.

Fe,?erger G* 3r0g von Nidda F-A* Jritsch )* 5eisenho+er G ;o?ina S* arXiv:cond!at* $&$&$7$v&cond-,at.str-el* 7 A0g* !2$$&".

4. odrig0eK / /* Pro++en Th* ;lo?et yne G G* Phys ev 6* 71 !2$$#" 1$44&$.

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)ol.19* 2$1& - Selected +ro, International on+erence on ecent Trends in Applied Sciences with /ngineering Applications

1$'

#. 5agotto /* Fotto T oreo A* Phys ep* &44 !2$$1" 1.%. 3ho,sii 5 I* Int G od Phys 6* 1# !2$$1" 2%%#.7. Saitoh /* (a,oto S* Taahashi 3 T* To?e 3* Ha,a,oto 3* 3i,0ra T* Ishihara S* aeawa S To0ra

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