Observation of complex magnetic behaviour in calcium doped neodymium manganites

Abstract

Crystal structure and magnetic properties of polycrystalline Nd1−xCaxMnO3 (x = 0.0, 0.2, 0.3, 0.33, 0.4, 0.5, 0.6 and 0.8) manganites were investigated. The fine structural refinement using GSAS was found to undergo a transition from Pnma reflections to Pbnm reflections associated with the Ca substitution at x = 0.3. The magnetic ordering of these compounds witnessed distinct magnetic phases with variations of Ca substitution. Magnetic ordering of the parent compound, NdMnO3, was found as A-type antiferromagnetic (AFM) in accordance with the earlier reports, which progressively undergoes to canted A-type AFM for x = 0.2, pseudo CE-type AFM for the intermediate compositions, i.e. x = 0.3 to x = 0.5 and CE-type AFM for x > 0.5. The x = 0.2 compound exhibited ferromagnetic like (weak AFM) behaviour, and the critical exponent study reinforced the magnetic inhomogeneity of the compound. Hysteresis curves of all the compounds measured at different temperatures implied the presence of metamagnetic like transitions for the intermediate compositions (0.3 ⩽ x ⩽ 0.5). Relative cooling power (RCP) value of Nd0.8Ca0.2MnO3 was observed to be 900 J Kg−1, at the higher magnetic field, making it a promising candidate for magnetic refrigeration applications.

Irreversible Meta‐Magnetic Transition in Charge Ordered Nd0.5Ca0.5MnO3 Manganite

“…The temperature at which onset of CO phase takes place in the material has been designated as T CO and as a consequence a broad cusp is visible in the temperature‐dependent magnetization curve. In the present case, it has been found that the cusp is around 240 K and the observed T CO value is in good agreement with the reported values for half‐doped NCMO manganite . The large anomaly found around T CO is also visible in the first derivative of FC curves around T CO (shown in inset of Figure (a)).…”

“…In the present case, it has been found that the cusp is around 240 K and the observed T CO value is in good agreement with the reported values for half-doped NCMO manganite. [7,26] The large anomaly found around T CO is also visible in the first derivative of FC curves around T CO (shown in inset of Figure 3(a)). Even though, the anomaly is not visible from M-T curves of nano sample, a zoomed derivative curve shows the signature of CO anomaly around 240 K (inset of Figure 3(b)).…”

“…These materials not only show a complex phase diagram but also exhibit an unparalleled range of couplings between charge, orbital, spin, and lattice degrees of freedom resulting in various competing interactions such as double‐exchange, super‐exchange, Jahn–Teller distortion, Hund's coupling, etc . The phase diagrams of small bandwidth manganites are highly complex, and they show magnetic and electronic phase separation, charge, orbital and spin orderings, etc …”

“…[4][5][6] The phase diagrams of small bandwidth manganites are highly complex, and they show magnetic and electronic phase separation, charge, orbital and spin orderings, etc. [7] Among many complex physical phenomena of manganites, the charge ordering (CO) is an interesting aspect in small bandwidth manganites due to strong interaction among electrons resulting in localization of carriers in different sites of the crystal structure. It is known that the Mn cation in manganites exhibits two valence states viz., Mn 3þ and Mn 4þ (for 0 < x < 1), wherein Mn 3þ ion acts as an electron donor and Mn 4þ ion acts as an acceptor in the context of charge transport.…”

Observation of enhanced magnetic entropy change near room temperature in Sr-site deficient La0.67Sr0.33MnO3 manganite

“…res.in; vasu.mutta@gmail.com; Tel: +91 4712515491 properties due to the difference in the average A-site ionic radius. [22][23][24][25][26][27] It is understood that, in doped manganites, the double exchange (DE) interaction via the Mn 3+ -O 2À -Mn 4+ ions is responsible for the ferromagnetic (FM) behaviour and the superexchange (SE) interaction through Mn 3+ -O 2À -Mn 3+ and Mn 4+ -O 2À -Mn 4+ ions are responsible for the antiferromagnetic (AFM) behaviour. This indicates that the strength of the competing exchange interactions and magnetic properties are eventually affected by different factors such as rare Earth substitution at the A-site, replacement of manganese by other transition elements, the introduction of deciency at A and A 0sites, etc.…”