Colossal Magnetoresistance, Charge Ordering and Related Properties of Manganese Oxides

Rao, C. N. R.; Raveau, B.

doi:10.1142/3605

Cited by 709 publications

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“…Ca, Ba, Sr, Pb or Bi etc.) were widely studied for their unusual magnetotransport properties, please see couple of review and references there in [1][2][3]. These materials gave rise to huge magneto-resistance (MR) just below room temperature.…”

Section: Introductionmentioning

confidence: 99%

“…In these regards there had been some trials in literature [4][5][6]. For example by increasing the amount of Mn 4+ through substitutions like RE/Ag [4,5], or increase in overall oxygen content [1,7], one could shift the T MI and T FM above/close to the room temperature. However one needs not only the room temperature T MI and T FM but sharper MI and FM transitions for meaningful MR at these temperature.…”

Section: Introductionmentioning

confidence: 99%

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Magneto-transport of high TCR (temperature coefficient of resistance) La2/3Ca1/3MnO3 : Ag polycrystalline composites

Awana

Tripathi

Balamurugan

et al. 2006

Solid State Communications

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We report the synthesis, (micro)structural, magneto-transport and magnetization of polycrystalline La 2/3 Ca 1/3 MnO 3 :Ag x composites with x = 0.0, 0.1, 0.2, 0.3 and 0.4. The temperature coefficient of resistance (TCR) near ferromagnetic (FM) transition is increased significantly with addition of Ag. The FM transition temperature (T FM ) is also increased slightly with Ag addition. Magneto-transport measurements revealed that magneto-resistance MR is found to be maximum near T FM . Further the increased MR of up to 60% is seen above 300 K for higher silver added samples in an applied field of 7 Tesla. Sharp TCR is seen near T FM with highest value of up to 15 % for Ag (0.4) sample, which is an order of magnitude higher than as for present pristine sample and best value yet reported for any polycrystalline LCMO compound. Increased TCR, T FM and significant above room temperature MR of La 2/3 Ca 1/3 MnO 3 :Ag x composites is explained on the basis of improved grains size and connectivity with silver addition in the matrix. Better coupled FM domains and nearly conducting grain boundaries give rise to improved physical properties of the La 2/3 Ca 1/3 MnO 3 manganites. Ag composites Ag is not substituted into main LCMO lattice but remain rather as an additive in the system. (280 K) is comparable to aligned thin films [6,8,15] of LCMO, and to our knowledge is the best one yet obtained for any polycrystalline mangenites. As far fixed temperature and varying field MR is concerned its shape is changed from U type to V type. And is maximum at all fields up to 7 Tesla at 300 K. Infact with an increase in Ag content the low T below 300K MR% decrease and the room temperature 300 K increase. For LCMO: Ag (0.4) sample the MR of up to 60% is observed in 7 Tesla field at 300 K. Even at low fields of say 1 Tesla the MR of up to 16% is seen.The results of magnetization and magneto transport of LCMO:Ag x composites can be summarized as follows: 7 1. Ag does not substitute into host LCMO matrix in our polycrystalline LCMO:Ag x composites but improved significantly the grain morphology of the host.2. The T MI and T c remain nearly invariant with increase in x (Ag content).3. The sharpness of insulator-metal transition increases dramatically with increase in x (Ag content) and high (15%) sharp TCR is observed for Ag composites 4. Though the MR is seen in all the samples right from 300 K down to 5 K, the same is negligible at 300 K and more at lower T for pure sample and is maximum at 300 K and least at 5 K for Ag (0.4) containing compounds. DISCUSSIONNow we try to explain in broad sense the main results summarized above, as far as (1) is concerned there are some very recent reports in literature, which deals with the LCMO and LCMO/ZrO 2 [20]. In all these composites the quality of the LCMO was deteriorated. In case of LCMO:Ag there is a good probability of Ag being distributed at grain boundaries and hence providing better connectivity of grains, which is seen in Fig. 2(b). In most of other composites [16][17][18][19][20] the addi...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Magneto-transport of high TCR (temperature coefficient of resistance) La2/3Ca1/3MnO3 : Ag polycrystalline composites

Awana

Tripathi

Balamurugan

et al. 2006

Solid State Communications

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“…Mixed phase manganites of the form R 1-x M x MnO 3 (R = La, Pr, Nd, Sm and M = Sr, Ca, Ba, Pb) are strongly correlated systems in which competing interactions give rise to a variety of interesting phenomena 1 , including colossal magnetoresistance (CMR) 2 and a large magnetocaloric effect (MCE). 3 First gaining attention in the 1950s, 4 manganites continue to excite interest in the scientific community from the standpoint of both application and basic understanding.…”

Section: Introductionmentioning

confidence: 99%

“…5 The push for energy-efficient magnetic refrigeration based on MCE has gained momentum in recent years, fueling further research into complex magnetic oxides. [1][2][3] Among the most intriguing properties exhibited by the manganites is the occurrence of spatial separation between regions of distinct magnetic ordering. [11][12][13] The sensitivity of such phase separated systems to a variety of parameters including electric and magnetic field, strain, doping, and particle size introduces the potential for a large degree of tunability in magnetic and structural properties.…”

Section: Introductionmentioning

confidence: 99%

“…5,14,15 Phase separation is most often observed between an insulating antiferromagnetic chargeordered (CO) phase and a metallic ferromagnetic (FM) phase. 1 Charge ordering refers to the periodic arrangement of cations of different oxidation states within a crystal lattice, a common phenomenon in narrow bandwidth manganites in which long-range Coulomb interactions overcome the kinetic energy of the charge carriers. 16 While the electron-doped manganite compounds temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Impact of nanostructuring on the magnetic and magnetocaloric properties of microscale phase-separated La5/8−yPryCa
Bingham
¹
,
Lampen
²
,
Phan
³

et al. 2012
Phys. Rev. B

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Bulk manganites of the form La 5/8-y Pr y Ca 3/8 MnO 3 (LPCMO) exhibit a complex phase diagram due to coexisting charge-ordered antiferromagnetic (CO/AFM), charge disordered paramagnetic (PM), and ferromagnetic (FM) phases. Because phase separation in LPCMO occurs on the microscale, reducing particle size to below this characteristic length is expected to have a strong impact on the magnetic properties of the system. Though a comparative study of the magnetic and magnetocaloric properties of single crystalline (bulk) and nanocrystalline LPCMO (y = 3/8) we show that the AFM, CO, and FM transitions seen in the single crystal can also be observed in the large particle sizes (400 nm and 150 nm), while only a single PM to FM transition is found for the small particles (55 nm). Magnetic and magnetocaloric measurements reveal that decreasing particle size affects the balance of competing phases in LPCMO and narrows the range of fields over which PM, FM, and CO phases coexist. The FM volume fraction increases with size reduction, until CO is suppressed below some critical size, ~100 nm. With size reduction, the saturation magnetization and field sensitivity first increase as long-range CO is inhibited, then decrease as surface effects become increasingly important. The trend that the FM phase is stabilized on the nanoscale is contrasted with the stabilization of the charge-disordered PM phase occurring on the microscale, demonstrating that 2 in terms of the characteristic phase separation length, a few microns and several hundred nanometers represent very different regimes in LPCMO. PACS: 75.30.Vn

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Colossal Magnetoresistive Materials

Maignan

2002

Encyclopedia of Smart Materials

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Magnetoresistance (MR) is defined as the relative change in the electrical resistivity of a material upon the application of a magnetic field. MR is positive for most nonmagnetic metals, and its magnitude is limited to a few percent, whereas MR can be negative in magnetic materials because the magnetic field tends to reduce the spin disorder. MR is of considerable technological interest. IBM is using the Permalloy (composition: 80% Ni and 20% Fe) MR of about 3% in a small magnetic field at room temperature for the magnetic storage of information. More recently, larger magnetoresistance also called giant MR (GMR) was observed in thin films of magnetic superlattices (for instance, Fe, Cr) for which metallic layers of a ferromagnet and a nonmagnetic material (or an antiferromagnet) are alternately deposited on a substrate. By doing so, the MR magnitude is increased by an order of magnitude. Small ferromagnetic particles deposited on a paramagnetic thin film also provide an alternative way to obtain GMR devices. For both material classes, small magnetic field applications (a few oersteds) are sufficient to align the magnetizations ferromagnetically and thus to induce a resistivity decrease originating in decreased scattering. In hole‐doped perovskite manganites magnetoresistance values of ∼ −100% in large magnetic fields (several teslas) have been discovered. These effects are called CMR to distinguish them from GMR. CMR has motivated a large number of experimental studies of these oxides in bulk (ceramics and crystals) and in thin films and also of theoretical work to understand the origin of the phenomenon. In this article, several representative examples of perovskite manganites are given to illustrate the richness of their phase diagrams. More particularly, the chemical key factor governing the CMR of hole‐doped manganites that contain 30% Mn 4 + and have the Ln 0.7 AE 0.3 MnO 3 formula are reviewed. The existence of Mn 3 + /Mn 4 + charge ordering in the Mn lattice for half‐doped manganites and also for Mn 4 + }‐rich compositions (electron‐doped, x > 0.5) are discussed. Finally, the possibility of obtaining CMR properties in Mn 4 + ‐rich manganites is shown.

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Colossal Magnetoresistance, Charge Ordering and Related Properties of Manganese Oxides

Cited by 709 publications

References 0 publications

Magneto-transport of high TCR (temperature coefficient of resistance) La2/3Ca1/3MnO3 : Ag polycrystalline composites

Magneto-transport of high TCR (temperature coefficient of resistance) La2/3Ca1/3MnO3 : Ag polycrystalline composites

Impact of nanostructuring on the magnetic and magnetocaloric properties of microscale phase-separated La5/8−yPryCa
Bingham
¹
,
Lampen
²
,
Phan
³

et al. 2012
Phys. Rev. B

Colossal Magnetoresistive Materials

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Colossal Magnetoresistance, Charge Ordering and Related Properties of Manganese Oxides

Cited by 709 publications

References 0 publications

Magneto-transport of high TCR (temperature coefficient of resistance) La2/3Ca1/3MnO3 : Ag polycrystalline composites

Magneto-transport of high TCR (temperature coefficient of resistance) La2/3Ca1/3MnO3 : Ag polycrystalline composites

Impact of nanostructuring on the magnetic and magnetocaloric properties of microscale phase-separated La5/8−yPryCaBingham1, Lampen2, Phan3 et al. 2012Phys. Rev. B

Colossal Magnetoresistive Materials

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Impact of nanostructuring on the magnetic and magnetocaloric properties of microscale phase-separated La5/8−yPryCa
Bingham
¹
,
Lampen
²
,
Phan
³

et al. 2012
Phys. Rev. B