Citation: Semaida, A.M.; Darwish, M.A.; Salem, M.M.; Zhou, D.; Zubar, T.I.; Trukhanov, S.V.; Trukhanov, A.V.; Menushenkov,V.P.; Savchenko, A.G. Impact of Nd 3+ Substitutions on the Structure and Magnetic Properties of Nanostructured SrFe 12 O 19 Hexaferrite. Nanomaterials 2022, 12, 3452. https://doi.org/10.3390/ nano12193452 Academic Editor: Yurii K. Gun’ko Received: 8 September 2022 Accepted: 29 September 2022 Published: 2 October 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). nanomaterials Article Impact of Nd 3+ Substitutions on the Structure and Magnetic Properties of Nanostructured SrFe 12 O 19 Hexaferrite Ashraf M. Semaida 1,2 , Moustafa A. Darwish 3 , Mohamed M. Salem 3 , Di Zhou 4 , Tatiana I. Zubar 5,6 , Sergei V. Trukhanov 6,7, * , Alex V. Trukhanov 6,7,8 , Vladimir P. Menushenkov 1 and Alexander G. Savchenko 1 1 Physical Materials Science Department, National University of Science and Technology MISiS, 119049 Moscow, Russia 2 Physics Department, Faculty of Science, Damanhour University, Damanhour 22516, Egypt 3 Physics Department, Faculty of Science, Tanta University, Al-Geish St., Tanta 31527, Egypt 4 Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China 5 Laboratory of Single Crystal Growth, South Ural State University, 76, Lenin Av., 454080 Chelyabinsk, Russia 6 Laboratory of Magnetic Films Physics, SSPA “Scientific and Practical Materials Research Centre of NAS of Belarus”, 19, P. Brovki Str., 220072 Minsk, Belarus 7 Smart Sensor Systems Laboratory, Department of Electronic Materials Technology, National University of Science and Technology MISiS, 119049 Moscow, Russia 8 L.N. Gumilyov Eurasian National University, Nur-Sultan 010000, Kazakhstan * Correspondence: sv_truhanov@mail.ru Abstract: In this study, SrFe 12-x Nd x O 19 , where x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5, was prepared using high-energy ball milling. The prepared samples were characterized by X-ray diffraction (XRD). Using the XRD results, a comparative analysis of crystallite sizes of the prepared powders was carried out by different methods (models) such as the Scherrer, Williamson–Hall (W–H), Halder–Wagner (H–W), and size-strain plot (SSP) method. All the studied methods prove that the average nanocrystallite size of the prepared samples increases by increasing the Nd concentration. The H–W and SSP methods are more accurate than the Scherer or W–H methods, suggesting that these methods are more suitable for analyzing the XRD spectra obtained in this study. The specific saturation magnetization (σ s ), the effective anisotropy constant (K eff ), the field of magnetocrystalline anisotropy (H a ), and the field of shape anisotropy (H d ) for SrFe 12-x Nd x O 19 (0 ≤ x ≤ 0.5) powders were calculated. The coercivity (H c ) increases (about 9% at x = 0.4) with an increasing degree of substitution of Fe 3+ by Nd 3+, which is one of the main parameters for manufacturing permanent magnets. Keywords: ball milling; Halder–Wagner method; Williamson–Hall method; Nd 3+ doping; nanohexaferrite 1. Introduction Historically, hexaferrite is one of the oldest materials used to make permanent mag- nets [1]. Since ferrites are oxide materials, hexaferrite magnets are quite resistant to cor- rosion and oxidation. In addition, ferrites are electrical insulators at room temperature, making them an interesting material for applications that create a lot of eddy currents inside a magnet. The raw materials are plentiful at a low price, which makes ferrites the most used material for permanent magnets [2]. Ferrites are used for applications that require high volume or weight, such as inexpensive electric motors, loudspeakers, etc., so the price should be as low as possible [3–5]. The doping of M-type hexaferrite (BaFe 12 O 19 , SrFe 12 O 19 ) is often intended to influence the inherent magnetic structure of this compound, whose magnetic characteristics are dictated by the occupancy of five nonequivalent positions in the lattice and their magnetic coupling via oxygen-driven superexchange interactions [6]. For instance, the magnetocrys- talline anisotropy can be augmented by a local increase in magnetic anisotropy due to Nanomaterials 2022, 12, 3452. https://doi.org/10.3390/nano12193452 https://www.mdpi.com/journal/nanomaterials