Magnetic compensation, field-dependent magnetization reversal, and complex magnetic ordering in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Co</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>TiO</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>

Nayak, Sisir Kumar; Thota, Subhash; Joshi, D. C.; Krautz, Maria; Waske, Anja; Behler, A.; Eckert, J.; Sarkar, Tapati; Andersson, Mikael; Mathieu, Roland; Narang, V.; Seehra, M. S.

doi:10.1103/physrevb.92.214434

Cited by 54 publications

(56 citation statements)

References 37 publications

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“…Also, a second‐highest intensity peak was noticed at

463.53

eV, which is associated with Ti‐2 p

_{1 / 2}

. This result confirms the existence of the

3^{+}

oxidation state of Ti instead of

{Ti}^{4 +}

in CTO (). The

{Ti}^{3 +}

peak positions are consistent with the previously reported data of

{Ti}^{3 +}

surface defects at

457.7

eV in the

{TiO}_{2}

system ().…”

Section: Resultssupporting

confidence: 71%

“…In general, the trivalent configuration of cobalt cation is not possible in the inverted‐spinel CTO = [

{Co}^{2 +}

(

{Co}^{2 +} {Ti}^{4 +}

)

O_{4}

]. However, in the present case we observed the signatures of

{Co}^{3 +}

contribution at the octahedral sites of CTO that may play a vital role on the magnetic properties (). This trivalent configuration also determines most of the optical and magnetic properties including the internal d–d transitions.…”

Section: Resultsmentioning

confidence: 45%

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Spectroscopic studies of Co₂TiO₄ and Co₃O₄ two‐phase composites

Nayak

Dasari

Joshi

et al. 2016

Physica Status Solidi (b)

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In this article, we report a comparative analysis of various spectroscopic studies including low‐temperature (25thinmathspacenormalKthinmathspace≤T≤300normalK) Raman spectroscopy of cobalt‐orthotitanate (Co2TiO4) and tricobalt‐tetraoxide (Co3O4), and their solid solutions false(1−xfalse) Co3O4+x of Co2TiO4 (0≤x≤1 (100 wt.%)). For all the lower and intermediate compositions, five Raman‐active modes were recognized at 689, 618, 518, 480, and 195cm−1 that are associated with A1g, Eg, and 3F2g phonon symmetries. Conversely, pure Co2TiO4 exhibits a broad spectrum of width ∼93.3cm−1 without any signatures of F2g(3) mode. At low‐temperatures (down to 25 K) the A1g and F2g peaks of both Co2TiO4 and Co3O4 shift toward the high‐frequency side with anomalies across the ferrimagnetic Néel temperature (TN ∼48±5K) and antiferromagnetic Néel temperature (TN∼ 30 ± 10 K), respectively. All the investigated samples exhibit two distinct bands at 576cm−1 (B1) and 665cm−1 (B2) in the Fourier transform infrared spectra recorded at 300±10 K, associated with the vibrational stretching of the metal–oxygen bonds of length ∼195.8 pm (B–O) and ∼185.4 pm (A–O), respectively. The intensity of these sharp bands gradually decreases as the crystal structure transforms from normal‐spinel (a=8.07 Å) to inverse‐spinel structure (a=8.45 Å). The X‐ray photoelectron spectroscopy (XPS) studies revealed that the Ti was incorporated into the octahedral B‐sites of inverse‐spinel structure of Co2TiO4. Interestingly, the XPS spectra of Co2TiO4 provide evidence of the trivalent character of Ti instead of tetravalent cationic configuration together with a weak Co3+ character at the octahedral sites. These results are discussed in terms of the binding‐energy (BE) difference between the O‐1s and Ti‐2p3/2 (Δ[O–Ti‐2p3/2] = BE(O‐1s) −BE(Ti‐2p3/2false)) and the mean chemical bond length lfalse[italicTi−Ofalse]. The peculiarities of all these results in consonance with the crystal‐structure (bond angles and bond lengths) and electron‐spin‐resonance studies are discussed in detail.

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“…Also, a second‐highest intensity peak was noticed at

463.53

eV, which is associated with Ti‐2 p

_{1 / 2}

. This result confirms the existence of the

3^{+}

oxidation state of Ti instead of

{Ti}^{4 +}

in CTO (). The

{Ti}^{3 +}

peak positions are consistent with the previously reported data of

{Ti}^{3 +}

surface defects at

457.7

eV in the

{TiO}_{2}

system ().…”

Section: Resultssupporting

confidence: 71%

“…In general, the trivalent configuration of cobalt cation is not possible in the inverted‐spinel CTO = [

{Co}^{2 +}

(

{Co}^{2 +} {Ti}^{4 +}

)

O_{4}

]. However, in the present case we observed the signatures of

{Co}^{3 +}

Section: Resultsmentioning

confidence: 45%

Spectroscopic studies of Co₂TiO₄ and Co₃O₄ two‐phase composites

Nayak

Dasari

Joshi

et al. 2016

Physica Status Solidi (b)

Self Cite

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“…As shown in the results of RBS (Table ), the Co 0.2 TiO 3.2 system compared to the nominal mode Co 2 TiO 4 , presents deficiency of cobalt atoms that may have contributed to a disorder in the system causing the appearance of the amorphous state. Thus, we can assume that the CTO layer would have a certain tendency to grow oriented in the plane (311) (inverse spinel and Fd‐3m space group), since it modifies the intensity of the main peak in its low crystallinity state …”

Section: Resultsmentioning

confidence: 99%

Study of Filament Resistive Switching in New Pt/Co_0.2TiO_3.2/ITO Devices for Application in Non‐Volatile Memory

Góis

Valença

Machado

et al. 2018

Physica Status Solidi (a)

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In this work, the authors present a study of the resistive switching effect (RS) in Co0.2TiO3.2 (CTO) in a thin film structure Pt/CTO/ITO. The identification of a structure of low crystallinity with different deposition times is seen in the diffractograms with a certain tendency of orientation in the plane (311) of the inverted spinel of space group Fd‐3m. Electrical measurements I–V highlight the appearance of RS effect predominated by unipolar filamentary mechanism. The retention of charge in the device shows good stability and separation of HRS‐LRS states with ROFF/RON ≈106 ratio. The authors are able to demonstrate that Co0.2TiO3.2 presents promising performance for application in non‐volatile memories.

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“…К р и с т а л л и ч е с к а я с т р у к т у р а и ф о н о н -н ы е м о д ы. Соединение Co 2 TiO 4 кристаллизуется в кубической пространственной группе Fd3m (№ 227, Z = 8), точечная группа m3m [8]. Параметр решетки a = 8.45 ¦ .…”

Section: теоретические аспектыunclassified

“…Co 2 TiO 4 является ферримагнетиком; при температурах ниже T C = 56 K происходит ферримагнитное упорядочение с точкой компенсации магнитного момента T comp = 32 K. При дальнейшем понижении температуры наблюдается магнитный момент, величина которого зависит от маг- нитного поля, насыщение не было обнаружено вплоть до полей 15 T [8]. Также сообщалось о наблюдении несораз-мерных магнитных структур, состоянии спинового стек-ла [7] и наличии магнитных кластеров [8,9]. Указанные эффекты, вероятно, вызваны разупорядочением ионов…”

Section: теоретические аспектыunclassified

Динамика решетки и электронная структура кобальт-титановой шпинели Co-=SUB=-2-=/SUB=-TiO-=SUB=-4-=/SUB=-

Просников¹,

Молчанова²,

Дубровин³

et al. 2016

Физика Твердого Тела

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Представлены результаты исследований фононных возбуждений и электронной структуры обращенной шпинели Co 2 TiO 4 , в которой ниже TC = 56 K магнитоупорядоченные ионы кобальта Co 2+ (3d 7 ) находятся в равном количестве в тетраэдрической и октаэдрической подрешетках. Исследовались монокристаллы с использованием оптических методов отражения и поглощения в широком спектральном интервале, раманов-ского рассеяния, а также метода диэлектрической спектроскопии. Изучена динамика инфракрасных и Раман-активных фононов, обнаружены особенности, связанные с наличием разупорядочения в тетраэдрических позициях. Зарегистрированные d−d-электронные переходы в области 3800 и 6300 cm −1 подтверждают координационные особенности ионов Co 2+ . Обнаружен рост диэлектрической проницаемости в области температур ниже 130 K.Работа выполнена при поддержке Российского научного фонда (проект № 16-12-10456).

show abstract

Magnetic compensation, field-dependent magnetization reversal, and complex magnetic ordering inCo2TiO4

Cited by 54 publications

References 37 publications

Spectroscopic studies of Co₂TiO₄ and Co₃O₄ two‐phase composites

Spectroscopic studies of Co₂TiO₄ and Co₃O₄ two‐phase composites

Study of Filament Resistive Switching in New Pt/Co_0.2TiO_3.2/ITO Devices for Application in Non‐Volatile Memory

Динамика решетки и электронная структура кобальт-титановой шпинели Co-=SUB=-2-=/SUB=-TiO-=SUB=-4-=/SUB=-

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Magnetic compensation, field-dependent magnetization reversal, and complex magnetic ordering inCo2TiO4

Cited by 54 publications

References 37 publications

Spectroscopic studies of Co2TiO4 and Co3O4 two‐phase composites

Spectroscopic studies of Co2TiO4 and Co3O4 two‐phase composites

Study of Filament Resistive Switching in New Pt/Co0.2TiO3.2/ITO Devices for Application in Non‐Volatile Memory

Динамика решетки и электронная структура кобальт-титановой шпинели Co-=SUB=-2-=/SUB=-TiO-=SUB=-4-=/SUB=-

Contact Info

Product

Resources

About

Spectroscopic studies of Co₂TiO₄ and Co₃O₄ two‐phase composites

Spectroscopic studies of Co₂TiO₄ and Co₃O₄ two‐phase composites

Study of Filament Resistive Switching in New Pt/Co_0.2TiO_3.2/ITO Devices for Application in Non‐Volatile Memory