Abstract
The structural, magnetic and magnetocaloric properties of La
0.7
Ba
0.2
Ca
0.1
Mn
1−x
Al
x
O
3
(0 ≤
x
≤ 0.1) perovskite manganite oxides have been investigated. X-ray diffraction (XRD) analysis using Rietveld refinement has shown that all of the samples under investigation crystallize with a rhombohedric structure in the
R
3̄
c
space group (N°167). Paramagnetic (PM) to ferromagnetic (FM) transitions have been observed in all of the synthesized samples. In addition, the maximum magnetic entropy change (Δ
S
maxM) for the
x
= 0 sample was found to reach ∼5.8 J kg
−1
K
−1
under an applied magnetic field of 5 T, which is sufficient for potential applications in magnetic refrigeration. For the same applied magnetic field (
μ
0
H
= 5 T), the relative cooling power (RCP) value is found to be 167 J kg
−1
. The critical properties of manganites La
0.7
Ba
0.2
Ca
0.1
Mn
1−x
Al
x
O
3
(0 ≤
x
≤ 0.1) are investigated through various techniques, such as modified Arrott plots, Kouvel–Fisher methods and critical isotherm analyses around the paramagnetic–ferromagnetic phase transition (
T
c
). The values of critical exponents, derived from magnetic data using the above methods, yield 0.246 ≤
β
≤ 0.253, 1.01 ≤
γ
≤ 1.12 and 4.76 ≤
δ
≤ 4.9 with a
T
c
of 300–350 K. The exponent values are close to those expected for tricritical mean field model ferromagnets with short-range dipole–dipole interactions.