Impact of nanostructuring on the magnetic and magnetocaloric properties of microscale phase-separated La5/8−yPryCa

Nicholas S. Bingham

¹

,

P. Lampen

²

,

Manh‐Huong Phan

³

et al.

Abstract

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

Visualization of a ferromagnetic metallic edge state in manganite strips

“…As shown in Supplementary Figs 8 and 9, pronounced edge phases have been consistently observed in these two systems as well, which strongly indicates that the observed edge phase is not caused by the edge strain effect. This means that the edge phase is clearly different from the strain-induced grain boundary effect observed in manganites bi-crystals 14,15 or polycrystals 16,17 . ARTICLE A plausible mechanism of the edge phases in the manganite strips is the broken symmetry effect of the CE phase.…”

“…These features make manganites the ideal system in which to study edge state physics among complex oxides systems. Although surface [11][12][13] and grain boundary effects [14][15][16][17] have been observed in manganites systems, it is very interesting to verify whether broken symmetry effect can introduce intrinsic edge states in manganites, especially when EPS dominates the system. For this reason, we have chosen a model system of La 0.325 Pr 0.3 Ca 0.375 MnO 3 (LPCMO) which has been well known for its striking large length scale EPS between ferromagnetic metallic (FM) and CE-type antiferromagnetic charge-ordered insulating (CE) phases 18 .…”

Interfacial room temperature magnetism and enhanced magnetocaloric effect in strained La0.66Ca0.34MnO3/BaTiO3 heterostructures

“…While information on the macroscopic magnetization can be gained from MCE measurements, interfacial properties are not easily decoupled from bulk properties, thus requiring a more local probe. It has been shown that colossal effects, such as CMR and colossal MCE, are enhanced when the material is in a phase-separated state, due to the rapid expansion of one phase that dominates over the other on application of a magnetic field [44][45][46]. Therefore, in order to fully understand phenomena induced at the interface, we employed x-ray absorption spectroscopy (XAS) combined with x-ray magnetic circular dichroism (XMCD), and xray linear dichroism (XLD).…”

A comparative study on phase co-existence of $$\hbox {La}_{1/4}\hbox {Pr}_{3/8}\hbox {Ca}_{3/8}\hbox {MnO}_{3}$$ in a polycrystalline bulk and thin film

“…The major difference between the M-H plots of the bulk and thin film is the metamagnetic behaviour observed in the case of the bulk sample. While increasing the magnetic field, the magnetization first saturates around 1.6 T which corresponds to the alignment of all the FM moments in the sample [12,20]. As the field is further increased, another rise in magnetization is observed which corresponds to the melting of the CO state into the FM state.…”