J Supercond Nov Magn DOI 10.1007/s10948-016-3946-8 ORIGINAL PAPER Effect of Monovalent Cation Doping on Structural, Magnetic, and Magnetocaloric Properties of Pr 0.85 A 0.15 MnO 3 (A = Ag and K) Manganites G¨ on¨ ul Akc ¸a 1 · Ali Osman Ayas ¸ 2 · Selda Kılıc ¸C ¸ etin 1 · Mustafa Akyol 1 · Ahmet Ekicibil 1 Received: 23 June 2016 / Accepted: 29 November 2016 © Springer Science+Business Media New York 2016 Abstract A systematic study on the effect of monova- lent cation doping on structural, magnetic, and magne- tocaloric properties of Pr 0.85 A 0.15 MnO 3 (A = Ag and K) samples synthesized by a sol-gel method has been carried out. The crystal structure and morphology have been worked by X-ray diffraction (XRD) and scanning electron microscopy (SEM) imaging measurements. The XRD results indicate that both samples have orthorhom- bic structure. Magnetization versus temperature measure- ments show that our samples display a ferromagnetic-to- paramagnetic phase transition with increasing temperature. The ferromagnetic-to-paramagnetic phase transition tem- perature (T C ) values were found as 74 and 116 K for Pr 0.85 Ag 0.15 MnO 3 and Pr 0.85 K 0.15 MnO 3 , respectively. The magnetic entropy changes were evaluated from isothermal magnetization curves measured at various temperatures near T C by steps of 4 K. The values of the magnetic entropy change were determined as 0.99 and 1.39 J kg −1 K −1 for Pr 0.85 Ag 0.15 MnO 3 and Pr 0.85 K 0.15 MnO 3 under external field changes of 10 kOe, respectively. Keywords Manganites · Magnetic properties · Magnetic entropy change · Magnetocaloric effect  Ali Osman Ayas ¸ aayas@adiyaman.edu.tr 1 Department of Physics, Faculty of Sciences and Letters, C ¸ukurova University, 01330 Adana, Turkey 2 Department of Mechatronics Engineering, Faculty of Technology, Adıyaman University, 02040 Adıyaman, Turkey 1 Introduction The magnetocaloric effect (MCE), described as cooling or heating of a magnetic material under magnetic field change, offers an alternative technology for refrigeration [1]. The magnetic refrigeration (MR) technology has basic advantages over a classical system such as not emitting environmentally harmful gases and being more energy effi- cient [2–4]. It would be possible to achieve mentioned advantages only if desired magnetic materials can be pro- duced. For this reason, MCE has been investigated widely to find a proper refrigerant material that can produce large entropy change when it goes through magnetization- demagnetization process [5–7]. So far, it has been reported that the large spontaneous magnetization and a sharp change in the magnetization with changing temperature are impor- tant requirements for magnetic material to possess large magnetic entropy change [8, 9]. The perovskite mangan- ites having the general formula RE 1−x A x MnO 3 (RE and A are a trivalent rare-earth cation and a divalent or monova- lent cation, respectively) have attracted much attention due to their interesting physical and magnetic properties such as colossal magnetoresistance (CMR) and MCE [10–12]. It is known that REMnO 3 is an antiferromagnetic insulator [13]. The magnetic and transport properties of these base sam- ples are strongly affected by the percentage of the divalent or monovalent cation ions, the ionic radii of these ions, and the preparation method of the samples [14, 15]. For RE = Pr case, in the literature, there are a lot of studies about the structural, magnetic, and magnetocaloric properties with divalent substitutions. However, the substitution of mono- valent (A = Na, K, Ag, etc.) elements by RE ions has been much less studied [13, 16–21]. Jir´ ak et al. reported struc- tural and physical properties of Pr 1−x A x MnO 3 manganites 0 ≤ x ≤ 0.15 for K [16] and 0 ≤ x ≤ 0.2 for Na [17],