PHYSICAL REVIEW B 101, 054413 (2020) Hydrostatic pressure influence on T C in (Ga,Mn)As Marta Gryglas-Borysiewicz , * Adam Kwiatkowski, Piotr Juszy´ nski, Zuzanna Ogorzalek, Konrad Pu´ zniak , Mateusz Tokarczyk, Grzegorz Kowalski, Michal Baj, and Dariusz Wasik Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, Warsaw, Poland Nevill Gonzalez Szwacki Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, Warsaw, Poland Jacek Przybytek Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, Warsaw, Poland and Institute of High Pressure Physics PAS, 01-142 Warsaw, Poland Janusz Sadowski Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, Warsaw, Poland; Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, Warsaw, Poland; and Department of Physics and Electrical Engineering, Linnaeus University, SE-391 82 Kalmar, Sweden Maciej Sawicki, Piotr Dziawa , and Jaroslaw Z. Domagala Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, Warsaw, Poland (Received 10 October 2019; revised manuscript received 30 November 2019; accepted 7 January 2020; published 10 February 2020) The influence of hydrostatic pressure on the Curie temperature T C of thin ferromagnetic (Ga,Mn)As layers is studied. New experimental data unambiguously point to both positive and negative pressure-induced changes of Curie temperature. The positive pressure coefficient is observed for samples with relatively high values of T C and can be quantitatively described by the p-d Zener model of carrier-mediated ferromagnetism within the six-band k · p formalism and the ab initio approach. First-principles calculations of structural, electronic, and magnetic properties of (Ga,Mn)As show that antiferromagnetic coupling of substitutional Mn atoms with interstitial ones may account for a decrease of T C under pressure in samples having a substantial concentration of interstitial Mn. DOI: 10.1103/PhysRevB.101.054413 I. INTRODUCTION Application of hydrostatic pressure in the studies of mag- netic condensed matter materials is a valuable tool to uncover the nature of ferromagnetic interactions [1–8]. It is espe- cially important in the case of carrier-mediated ferromagnetic interactions, as pressure can efficiently change the carrier concentration [7], degree of their localization [4], as well as details of band structures, e.g., allowing the side Bril- louin zone minima to be populated [1]. (Ga,Mn)As belongs to this group of materials, being one of the best studied diluted magnetic semiconductors so far [9–11]. The best (Ga,Mn)As samples show ferromagnetic ordering with the Curie temperature (T C ) reaching as high as 190 K [12–15], being below room temperature but reasonably high for proof- of-concept studies. It was proposed that valence-band holes mediate ferromagnetic coupling between Mn acceptors in this system, and that ferromagnetic properties can be described in terms of the multiband p-d Zener model [9,16], the proposal verified quantitatively or semiquantitatively by a number of * mgryglas@fuw.edu.pl experiments [10,11] and ab initio works [17,18]. At the same time, a proximity to the metal-insulator transition [16,19–21] and complex material properties make the understanding of several findings challenging, particularly in highly resistive, nonmetallic samples. Previous studies of diluted ferromagnetic semiconductors demonstrated an increase of T C with hydrostatic pressure in both (In,Mn)Sb [22] and in almost all studied (Ga,Mn)As films [23–26]. This increase of T C in (Ga,Mn)As was success- fully explained by ab initio computations [27] and found con- sistent with simple considerations in the frame of the Zener model [24]. However, in a high-resistivity (Ga,Mn)As sample with a relatively low value of T C , the sign of dT C /dp was dependent on a method used to determine the magnitude of T C . In this paper we report on the accurate evaluation of T C ( p) for a series of (Ga,Mn)As films employing recently proposed methods of the T C determination from weak-field magnetore- sistance measurements [28]. We confirm that the sign and magnitude of dT C /dp for samples with high magnitudes of T C is in accord with the expectations of the p-d Zener model. Fur- thermore, we unambiguously show that the negative pressure coefficient is present for a certain class of samples. We carry out ab initio computations, which demonstrate a sign change 2469-9950/2020/101(5)/054413(10) 054413-1 ©2020 American Physical Society