## 1 Introduction  
M-type (MeFe\({}_{12}\)O\({}_{19}\) Me: Ba, Sr) hexaferrites have been applied for ceramic permanent magnets due to their cost-effectiveness, chemical stability, and notable hard magnetic characteristics, including high \(M_{\rm S}\) and high \(H_{\rm d}\)[1; 2; 3]. Thus, these permanent magnets have been used for the motor components of automobiles, household washing machines, air conditioners, etc. Among various fabrication processes employed to prepare M-type hexaferrites [1; 4], the solid-state reaction is a commonly employed method in industrial manufacturing due to its cost-effectiveness and suitability for mass production. The performance of a permanent magnet is normally evaluated on the basis of its \(B_{\rm r}\), \(H_{\rm d}\), and \((BH)_{\rm max}\) values, which are closely related to intrinsic properties, such as \(M_{\rm s}\) and \(H_{\rm d}\)[1; 2; 3; 4; 5]. The intrinsic properties of \(M_{S}\) and \(H_{a}\) for M-type hexaferrites depend on the cation substitution composition and site occupancy in the unit cell [1; 3; 4; 5]. M-type hexaferrites consist of the stacked structures of spinel (S, Fe\({}_{6}\)O\({}_{8}\)) and hexagonal (R, MFe\({}_{6}\)O\({}_{11}\)) blocks, represented as SRSR, where the asterisk (*) denotes a 180\({}^{\circ}\) rotation around the \(c\)-axis. The crystallographic sublattices of Fe\({}^{3+}\) in the M-type structure are categorized into five sublattices: \(2a\), \(2b\), \(4f_{1}\), \(4f_{2}\), and \(12k\) sites. The spin magnetic moments of Fe\({}^{3+}\) ions at the \(12k\), \(2a\), and \(2b\) sites align parallel to the \(c\)-axis, while those at the \(4f_{1}\) and \(4f_{2}\) sites align antiparallel to it. Consequently, this arrangement results in a net magnetic moment of 20 \(\mu_{B}\) per unit cell at 0 K [1; 6]. The \(M_{S}\) value can be improved through the substitution of cations like Co\({}^{2+}\)[7], Zn\({}^{2+}\)[8], Al\({}^{3+}\)[9], and Ti\({}^{4+}\)[10] for the Fe\({}^{3+}\) sites. On the other hand, \(H_{a}\) can be increased by substituting rare earth elements for the Sr site, such as La [11], Nd [12], and Sm [12]. While a simultaneous improvement of both \(M_{S}\) and \(H_{a}\) values via a single element substitution has never been reported [1; 8; 9; 10; 11; 12; 13], among various substituents explored, La-Co co-substitution has been reported to be very effective for the enhancement of \(H_{a}\) without a significant reduction in \(M_{S}\)[14; 15; 16; 17; 18; 19; 20]. The magnetic properties of M-type bulk magnets can be influenced by various factors, such as the sintering density, the average grain size and distribution, and the \(c\)-axis alignment of grains, in addition to chemical compositions [21]. The magnetic properties of sintered samples are largely influenced by the sintering additives [22; 23], sintering temperature and time [24], and atmosphere [25; 26]. High sintered density and high grain alignment along the \(c\)-axis dominantly contribute to an increase in \(B_{r}\), while the size and distribution of grains with multiple domains have an inverse relationship with \(H_{ci}\). The sintering additives of SiO\({}_{2}\) and CaCO\({}_{3}\) have been commonly used for M-type hexaferrites not only to achieve high sintered density through a liquid-phase sintering but also to suppress grain growth [22; 23]. Meanwhile, the MFP process is a highly effective technique for the fabrication of high-performance permanent magnets. This is achieved by aligning the magnetic easy axes of individual particles parallel to the external magnetic field during the pressing process [3; 27]. The \(c\)-axis alignment of M-type hexaferrite particles via the MFP method significantly improves the squareness of the demagnetization curve of a sintered bulk sample, resulting in a marked enhancement in both \(B_{r}\) and \((BH)_{max}\). The effectiveness of the MFP method extends to the industrial production of various permanent magnets, such as M-type hexaferrite [28], SmCo\({}_{5}\)[29], Sm\({}_{2}\)TM\({}_{17}\)[30], and Nd-Fe-B magnets [31].